There used to be a way around this using one neat trick...
When I started this job 25 years ago, all the HR papers were sent home with us to be brought in signed with required documents the next day. A colleague, apparently smarter than me, took advantage of this to print out superficially identical forms but with pesky things like non-competes reworded to be meaningless. They never caught on.
Non-competes are no longer enforceable in my state (Illinois) for those making less than $75k US (about 60k GBP), though I make a bit more than that. Colleagues have left for direct competitors before with no repercussions, so they're really not enforcing it unless you directly take trade secrets with you.
The one they do enforce is if I were to leave and go to a supplier, I can't come back on-site to my current employer for business until a year later, which does make some sense.