> Then they went legal trying to prevent me working for a competitor.

Was threatened with that early in my career after I resigned, I just replied "Check my employment contract, Good luck with that".

They where chaotically unorganised and the contract had no non-compete, they are enforceable in the UK but it's quite uphill to enforce an overly broad one (up to and including it just been nullified if you go too broad) and they have to show good evidence why it should be enforced.