I would plant a new bed on fresh ground if you have somewhere for them. Close to a grass edge is good as they are only invading one way into bare soil the other side. I find that hoeing keeps them in check. And I do think that they sound ready for a fresh start, you could use suckers for replanting any time until March.
Another possibility is to spread 2-5kg/square metre of rockdust on the existing bed to reinvigorate them, I have read that it can work. B&Q sell it now under ‘Verve’, £6 for 10kg.