Nicehash Quickminer is probably the easiest option - You can be up and running in minutes. You may want to set up an account on Coinbase to transfer currency to, which allows for easy payouts to a paypal account.
A word of warning - VRAM temps on the 30 series cards do get a mite toasty. I swapped out the thermal pads on mine for some 12.8 W/mK pads, which knocked 20 degrees off the VRAM. I also got a bunch of cheaper thermal pads to mount some passive heatsinks on the card's backplate which keeps the VRAM in the low 80s when producing ~ 120MH/s. It's a warm day and it's sitting at 84 degrees on the VRAM and 53 on the GPU, in an ITX case.
Good airflow and the passive sinks could be enough to get by if you don't fancy stripping down a £1400 card. Afterall, the more recent 3090s were shipped with marginally better pads than the originals, but I'm an inveterate tinkerer and couldn't help myself. Post-Op, my first 3090 far outperformed my more recent card in the thermal stakes, until I replaced the pads on that one too - they ran pretty much identically before I sold the first one.