Flowery, as ever, is spot on.
I had a horrendous situation at work last year, and was desperate to leave. It was constructive dismissal with bells on! However, I couldn't take the chance of flouncing out as I needed the money. Once I had a sniff of a job offer, I did though. I had plenty of evidence of my boss' appalling behaviour. HR were well aware I had been treated dreadfully by him....it is a long story.
Anyway, I knew that if I took it the ET, I would get nothing...my new job pays a lot more. But I wanted to make him sweat. So I resigned and claimed (in the email) constructive dismissal. I had an exchange of emails with the external solicitors (expensive US firm), and one day had 4 letters on the door mat. I had 3/4 telephone conversations with them. I knew this was costing my boss a lot of money. I also got immense satisfaction from knowing that a lot of people had seen my letters which set out exactly what an arse he was.
After a few weeks we agreed a compromise agreement and I received tax free a good sum of money (equivalent to about 3 months usual pay).
The thing is that I have a quite a bit of employment law experience and so knew what to do and what buttons to press. If I had appointed a solicitor, the money I won would have been eaten up very quickly. I did speak off the record to some employment solicitor friends, and also to a couple of solicitors who I considered appointing at one stage (I thought that having letters from a serious firm might make my boss take me more seriously), but ultimately dealt with it myself.
It was a win win for me. But don't underestimate the stress that you could go through. My DH was seriously worried - but delighted at the ultimate result!