Onkyo M-508 Stuck in Protection Mode

I have a friends Onkyo M-508 which is stuck in Protection Mode where the meter lights stay orange and refuse to go green. I took the covers off and it was totally full of dust and dirt. blew it all out with low pressure compressed air and cleaned the circuit boards with board cleaner but made no difference. I am no way knowledgeable enough in this sort of electronics to go any further with this so can someone recommend a repairer in the UK ( preferably South West as its too heavy for delivery unless desperate ) who can have a look at this please as its too good to be consigned to the scrap heap.