I am aware we are closing in on this cycle, maybe another 6 months max give or take if we go by traditional knowledge... Right now I am looking to take a few low level punts... Just £500 here and there with 5x to 10x... a few (imo) low risk trades considering where we are in the cycle.
Someone already mentioned Coinbase or Kraken above. Have you tried them? Seems like you can access leverage after you declare that you are qualified as high net borrowers (details probably on their help page)[1]. Sounds like you need to get approved before you can use them, but that should be expected if the regulations are as strict as you said above. CMIIW.
[1]
https://support.kraken.com/articles/margin-trading-for-clients-in-the-united-kingdom