Funeral dress help

[LongingToBeByTheSea]

I've just got out of hospital and need to find a suitable outfit for a close family member's funeral this week. I have a non existent budget and it must be of the traditional, black formal type.
I usually dress very casually (jeans T-shirt etc) so have very few smart dress options. Not helped by the fact I have put on weight in the last 2 years so none of my old clothes actually fit. I'm now a size 14.
Please help me look put together and not let 'The side' down, stylish people!

Thank you everyone. I've ordered a couple to try as the charity shop closest didn't have anything suitable.
@MumofSpud I'm so sorry for your loss

When is the funeral?

@MumofSpud It's Wednesday

I was just about to recommend the Asda Polka dot dress!
I bought a similar one from New look back in the summer
I'm very sorry for your loss

Black opaque tights (go for 120 dernier, as the 60 and 80 deniers aren't what they used to be!) and a long sleeve, round neck, black/charcoal jersey smock dress. New Look do loads of this type of dress very inexpensively and they are comfortable. Add a necklace (can't go wrong with a cheap pearl necklace) and a dark coat. Any reasonable black shoes or ankle boots, except trainers. You could probably get the whole outfit of dress, necklace (charity shop if you don't have one already) and tights for £25 and the dress and tights will be comfortable enough to wear around and about afterwards.

Can't do links but if you look online at New Look and search for Black Long Sleeve Jersey Mini Dress you'll see quite a few options. A longer sleeve will stop it looking too casual.