I've got myself in a pickle for telling a lie

yes that’s right, the real problem here is your abundance of good qualities and remarkable willingness to help

Sorry, I realise it's their money! So not grabby.

This makes it look like you intended to just keep the money.
You do know what happened. Making it vague means they might blame someone else. Or if things don’t add up, they’ll suspect you and won’t trust you from now on.

Are you a compulsive liar, OP ? Because this might get you in another pickle.

Tell the truth, apologise, get her some flowers or chocolate and maybe even laugh at your silliness over a coffee.
They will understand your reasons for overlooking the gift-buying.

But people don’t like liars.

Don't drag the poor cleaner into it!

Just buy the gift, hand it in and fess up to everybody. You're sorry, it was just easier to say you'd handed it in, the recipient was away anyway, blah blah blah.

So what if they think you're an eejit? Maybe they won't ask you to do any more favours in future - I'd be happy with that if it was me.

Don't start accusing the cleaner of moving it. The cleaner is completely blameless.

Just tell the truth, it is totally understandable. The stress of Christmas is enormous and you were doing someone a favour. Just buy the gift asap and take it round, no drama, you shouldn't feel bad, life is stressful enough, if they don't understand, don't worry about it, at least they won't ask you again.

Don’t say you don’t know what’s happened- the giver might alert the intended recipient that something went missing from their home and they should be alarmed!

Either fess up or say it’s in a different part of the house (if you can get it there that is)

I wonder why the second family member has taken it upon themselves to go round there and look for it and report back to the first family member. That's quite an odd thing to do.

Except for the minor detail that she wasn't accused of stealing. And the additional minor detail that, as of today, she essentially has stolen the money (she took money but hasn't used it to actually buy the present).

You made an honest mistake. And they shouldn't be so grabby.

This is such a silly way to deal with it, that potentially opens you up to much worse problems.

I understand being busy and telling a white lie. But there's no excuse for continuing to lie.

It's also in my opinion quite cowardly to justify your poor behaviour by moaning about having been asked to do the favour. If you didn't want to do it, you should have said no.

I wouldn’t do that, you said you dropped it to the house so they will probably still investigate / query the recipient about it and where it has gone and someone like the cleaner could get the blame
Go to the house tomorrow early and put it in the garage or somewhere where you think the relative hadn’t checked

I think the suggestion from @Fetburzswefg above is spot on as it is truthful and therefore straightforward.

You have to come clean. It’s by far the best way, even though it feels awkward and embarrassing. Just say something like ‘I’m really sorry about this but in the pre-Christmas rush I didn’t have time to sort drop the present round. I told you I had done it so that you wouldn’t worry, and I intended to sort it before X returns from holiday. I will drop the gift off tomorrow if you like, or I totally understand if you would just prefer me to return the money. Again I’m really sorry about this.’

Giving back the money makes you look like you have been caught out stealing from them (which you kind of have). Just say you did drop it round but couldn’t see anywhere safe to leave it, so you put it back in your car boot and completely forgot about it, and then just take it round and go on with your life..

Be honest. Say you forgot over Christmas, it is in hand now, including buying it etc, then drop it off.

Stop bloody lying more! It's getting worse and snowballing! What's your name, Pinocchio?! You will have a nest at the end of your nose soon... "I've got no strings to hold me down..." 😅

Don't lie. One way or another you will make this worse.

Just tell the truth.

'It's my mess.
I should have said when you asked me to do it that I couldn't as I was really pushed for time. However, I didn't and said I would do it. As I knew would happen, I didn't get it done before Christmas. I thought that, as they were away, I'd do it before they got back.
I then stupidly said it was all done when you asked me because I didn't want you to feel I'd let you down. I intended to take the gift tomorrow to welcome them back.
What would you like me to do? I can take the gift tomorrow, as I planned, or if you'd prefer, I can return you the money and you can get them something yourself.
Sorry to have created this confusion. Lesson learned and I certainly won't say yes to things I can't do on time again.'

Just come clean! Be honest. Handing the money back makes you look far worse.

I hate it when friends or family ask me to do their running around for them, like I have more time in my life than they do. It’s wasn’t your responsibility to buy the gift and then deliver it, it was their job to do that, buying someone a gift is a personal thing, and the recipient assumes they have put thought and time into it, and not just passed the job onto someone else.
Don’t feel guilty for lying, just drop the gift in and say, oh yes, I left it behind the - - -, I guess you didn’t see it.
I hope they appreciate you, but next time I would politely say ‘Sorry, I simply don’t have the time, maybe you can ask Rudolf or sort it yourself’

OMG don't do this!!! It makes no sense and definitely makes you look like you were just going to keep the money. Just tell the truth - at this point it's by far the least bad option. It's a bit silly but not unforgivable.

Just tell the truth as you've told it in your first post. Apologise profusely and buy your friend some flowers. Also buy the gift and take it round.

Tell the truth and shame the Devil - Don't lie..People don't trust people who lie, and you will be respected far more if you fess up.

I agree with many previous posters here - confess what happened.
Do not tell more lies.

Like @Quinlan wrote, what if they accuse someone of stealing the item?

I mean, you didn’t just lie - you kept the money and didn’t even buy the item let alone deliver it. Now you’re going to tell the person you ‘don’t know’ what happened? Another lie!

Absolutely do NOT do this! So the giver will think you are down £40? They will likely say that you shouldn’t be out of pocket when you’ve done them a favour, so then they’ll give it back to you and you’ll feel even worse! And they’ll start trying to investigate who has nicked it. You will end up in even more of a pickle!

That is a very good point. This could really explode. Stop telling lies OP!