Safest UK Crypto borrowing

I traded some cryptocurrency last year which generated a capital gain and now have a tax bill to pay.

I have always custodied my own crypto in cold storage because i know people who lost coins when MtGox collapsed and then lost some myself when Cryptsy collapsed.

Rather than sell some crypto to pay the tax bill I am looking into borrowing against it. Through my own research i have come across Nexo and Sygnum. In both cases I would have to transfer around twice as much crypto to them to hold and accept the increased risk of trusting my bitcoin to someone else rather than self custody.

Are Nexo or Sygnum safe places to store crypto?

Are there better ways to borrow against your crypto in UK?

Is there anything else i should know?