like Karl says, do it yourself but read up on it and take your time. preparation is the key. £270 is very excessive btw.
sand the grills to key the surface - use a scotch pad to help you get into the grooves.
wash with soapy water and let it dry naturally
spray in a warm room with no wind
lots of light even coats, 15 mins apart
finish with lots of light even coats of lacquer.
use plastikote paint as it sticks to plastics really well. good luck