Found a reference to a 12v bulb on a forum, ordered 2 off eBay, took the head and bulbs to a local music shop lunchtime, went back by 5pm.... Guy says they were the wrong bulbs, showed me a far bigger bulb like a small tube with wire each side, says he had to slot the
amp out of case, take all the knobs, fixings etc off the front of the head to get at the VU ...... Then says that he soldered on the 2 bulbs instead and here it is back for £20. Meanwhile still awaiting a response from the ashdown techs :-(