does anyone know if a hope tech m4 caliper will work with an avid is mount adaptor ?

All mount adapters are standard and work with anything (unless I’m being stupid).

They aren’t all the same, but I have used a hope one with formula brakes, but an avid one wouldn’t work with formula…

Not sure if that helps you though, but I’d hazard a guess that it won’t work

not the same setup as yours, but i got a hayes adaptor that doesnt fit a hope caliper – well it fits, but the disc rubs on the fork post mount.

Avid ones are fussy- it will work technically, but you will need to run them without those washers that come with Avid brakes (the offset for them is in the caliper, not the mount). So, none of the washers seen here-

thanks spokescycles, hopefully should save me trawling around all sheffield bike shops tomorrow and go for a ride instead 🙂