I've done mine. DH now doing his while keeping up a grumbling running commentary on how awful it is a) that he's having to do it at all and b) now shit the form is (I didn't think it was so very bad).
Not too awful apart from the refusal to accept my second dose QR code as proof of vacc status so I will presumably be put in some sort of delinquents' queue and asked to show it at St Pancras when we get off the train.
For testing kit it just asked for a package ref number - and I'd added the children as minors travelling with me by then so if it had wanted unique identifying numbers for each and every individual it would have asked for them.
I've got a cold white wine on the go which I must say helped enormously.