Right Poonli I've been through three disciplinaries (not me, but as a senior manager/witness) recently so know all the legal ins and outs of what the employer has to do (it's really very very hard to sack someone).
If you've been there more than 12 months, and it sounds like you have, there are certain things they should have done/prove. With any disciplinary that is not down the instant dismissal route (basically malicious behaviour) before it gets to a hearing we have to have issued a notice of concern - this is often verbal initially, and then in writing as a second phase. There will be a time limit on this - I think it's 6 months - so he shouldn't be able to use anything from last year against you anyway. If you go down the disciplinary route (which you should because you haven't done anything wrong) they will have to prove (with documentation) that you haven't met the minimum standards required of you. Have you had a performance review or development review recently?
Please, please do not just leave. At the very least you might get reach a compromise agreement with them which generally means a payout. You can't legally just get rid of people any more, although I appreciate you probably won't want to work in that environment anyway. Call the citizens advice bureau - get something (anything) in writing from him that you can show them. You're entitled to representation at a disciplinary hearing as well by the way. He's just trying to scare you with the stories of suing people for £60k - what would he sue you for?!
He should also give you written formal notice of disciplinary processing starting, with a timeline - you're entitled to 72 hours notice before the hearing.
I think we have some HR professionals on here so I hope I haven't got anything wrong. We use an employment lawyer and we absolutely have to follow the letter of the law. As I said, it's really really hard to get rid of people unless they've been in massive breach of their contract or stealing or something - we recently had to go down a redundancy route rather than disciplinary for someone who was underperforming rather than going down the competency route where you have to give them time to improve/offer training/support etc - none of which I assume have been offered to you?
Definitely CAB as a first stop - I know our employees have used them to get advice about the process.
Good luck. If you have any specific questions I can try and answer them but I think the first step is to get him to put things in writing (we have to set out 'the case' against the employee, with evidence in the letter than informs them we're starting disciplinary proceedings against them). You can then take this to the CAB and go from there.