that's the problem with a "Quote" rather than an estimate - strictly speaking you should honour the price where an estimate can result in the price going up or down.
If it were me I would carry out the cleans - £4 x 5 properties is hardly breaking the bank is it ? - do 6 cleans then increase the price to bring them into line with your other work - depending on the canvasser agree he only receives 50% for them or nothing or gets full price but provides replacement FOC - I'm sure that would more than cover the "loss"
Hes requoted one of the jobs at a higher price, the other ones ive agreed to do at agreed price but will increase after 3 cleans. Hes discounted all the jobs that were under price. The work is really compact, so its not breaking the bank. Yeah the jobs are £4 under, but all said and done its compact canvassing, so hourly rates should still be pretty good as virtually no travel time between jobs.
We do lots of work where jobs are priced £5+ higher but its because theres like 2-5 mins driving between each job, so again i can allow for lower pricing on the condition thats its compact, and again ill just up the prices after a few cleans worst case!