As a follow up if anyone's interested, I've been into the Marshall service department today, and it was indeed a defective input jack. All replaced and checked over for 20 quid! Happy indeed. Also in the mean time I've put in new preamp tubes I went with TAD 7025 r080 in V 1,2 and 3, and a sovtek 12ax7LSP. Sounds good so far. I've also had a rejig with my pedal board. Now I'm running an MXR micro amp first in the chain (of overdrives) set so it's just pushing the input so a nice gritty clean sound I'll probably run this on all the time. Then a Moore hustle drive again set quit mild on its ld setting, then a TC electronics Dark matter, again not masses of gain dialed in, and finally a tone city comp engine compressor. Now I'm using this as a boost and it works pretty well also thickening the tone in the process. I have it set with a lot of level low attack and the comp dialled to about 3/4. At the moment. Obviously I can also use this for other more traditional uses. Overall really pleased with it. I may do a demo vid when I get chance in the near future.