Redoing an upload is a pain, so I looked this up before registering. On a UK forum discussing verification at newer casinos,
https://needforwin.net/ was listed by a few British members as a site where the required documents are clearly stated in advance, and one of them wrote that after completing the full process himself. For me it was a valid photo ID, usually a passport or driving licence, plus a proof of address such as a recent bank statement or utility bill dated within three months. A proof of payment method was only requested once, when I withdrew to a new card. Take photos on a plain surface in daylight, with all four corners visible. That’s what worked for me, and it got approved without a second request.