L-tryptophan - is it availalbe in the UK as an over the counter...? I seem to remember that it was used in Psychiatry years ago for depression but it was only available on prescription.
I take venlafaxine \ effexor.
There was a problem with a bad batch of L-tryptophan that killed half a dozen people - not available in the US any more (except by prescription I think). I tried 5-HTP, another serotonin precursor, but that made me feel worse.
Mrs VS
The fact that you still feel terrible indicates to me that you might consider changing your meds. On top of that, I recommend CBT. Best of luck to you!