Thanks all... I'll have a go at the suggestions. Just weird it's come along suddenly after I've been playing for 22 years... oh well.

Some sort of padded chair and back posture would be the ones probably leading the field, I'll just have to pay more attention. I do play standing up most of the time, but if you're spending the day recording, a chair is good... ;)

I've tried sitting on my bed as well - same thing happens. Might be an excuse to buy myself a nice new chair.... maybe with a fridge in the arm rest... mmmm