A big deposit will ping a SAR off to SOCA. They'll probably look at it and keep an eye on your account for a few weeks but a one-off will generally fall through the net. £15k won't touch the sides. You can just say you sold a load of stuff, car, watches, furniture... to raise money for a deposit on a house. The bank won't call you on it unless it's all new notes. You need to make sure the cash is legit though, as in it's not fake. If it is you're getting a one way ticket to the slammer if you try deposit that ****. You could just spend the cash, get a load of work done on a house, 30k is worth a lot more to tradesman in cash.
Did it twice. First one was a stepfather who battered his 3 year old to death with a pool cue - no good to sit through that at any age but I was 19 FFS! Second stint was handling stolen goods and some bloke headbutting an opponent during a 5 a side match which was a bit of a laugh to be fair..
First one I did was the bloke who found the bin bags full of weed. That was quite good fun. But the other two were one for armed robbery on a post office and another for attempted murder by some black kid with a blade who took it on himself to go to another postcode and ‘put a notch on his block’. Remember seeing loads of hood rats in the public gallery looking down at the jury in that one and thinking it could be me next if we find this kid guilty. The case got thrown out for some reason, don’t know what the details were but something came up that compromised the case. I was mightily relieved to be honest.