So, having had time to crunch the numbers, here's the breakdown of how much it cost to stay in North America for 90 days (just in case you're thinking of going there). All values are GBP converted at the time of purchase.
So, Canada was nearly twice as expensive to stay than USA. We were in Canada for one month longer but were HelpXing for two months. Snowboarding in Canada is an expensive pasttime!
'Food' includes all general stuff which might come from a supermarket... and I think we missed a few laundry visits - i don't think we smelled that bad.