Thanks for that info , dont suppose you know what i would google when looking for staceys online as i havent heard of that company , i have just been dealing with hodge clemco up until nowTry and get quotes for someone to come and blast the front of your house, you'll know the area so you'll get an idea of how other people charge. Charging by hour may be best, give the customer an estimate (rather than a quote) to cover yourself for snags.
I've come a cropper on wheels in the past through not knowing how tough modern paints are!
With your figures you're only allowing £20 ph on top of grit & fuel, you've got all your other overheads & expenses, plus wages and you need to allow for the time you're not actually blasting
Consider using crushed glass at £100 per ton from Stacey's. That works out at £55 per ton for the grit (in bulk bags) plus carriage. They charge carriage at cost and for the size of stuff you're looking at you could order a few tons at a time.