Help, advice needed.

[FreezerGeezer]

Well mrchatts, my thinking is like this:

compressor list £128. So you put 50% on, and it's near £200. Presume it comes charged with oil.
Assuming a burnout, or sludged oil, you need new refrigerant. Let's say about 5 Kg, to allow a couple of changes if neccessary. Assuming £4.50/Kg for R134a, that adds £22.50. Reclaim cleaning is another £25. Small OFN about £16. Total so far £255.50
Then there's your travel. Let's assume 50ppm, and assume that you rack up 100 miles on the job for £50. Then you have a day's labour, at £30/hr for £300.
So there you are - already over the £500 mark. No doubt you won't do 100 miles for the job, and you may not allow a full day's labour. Or maybe you don't charge milage. But however you look at it, it's going to be the thick end of £500 to do the job properly.

I'm not actually responsible for raising quotes where I work, but the above looks like a reasonable estimate to me. You may all fall about laughing if you like!

I agree with needing to check the condenser out. Of course, this would add a little to your costs!