Struggle to find thirds in the UK?

We are a mid 20s couple with just over a years experience in this amazing lifestyle and thoroughly enjoying it so far.

We’ve found a couple of reliable and experienced guys that we’ve been seeing over the last 3/4 months but struggling to find new guys that she is attracted to, have experience and reliability.

Is there any sites or apps that could be recommended? We’ve tried Reddit and a few dating sites but is there somewhere better to find what we are looking for?

Thanks