I have found some Michelin Country Rock MTB Tyre for my mountain (full suspension bike ) but they are 26x 1.75. My tyres on the bike are 1.95 and 2.10 - will the 1.75 fit.These https://www.chainreactioncycles.com/michelin-country-rock-mtb-tyre/rp-prod8547 very cheap but seem just right for the riding I will be doing.
I would expect it to fit. A rather conservative chart of which tyres fit which rim width (1.75" is 47 mm when it comes to tyre sizing standards):
https://bike.bikegremlin.com/285/bicycle-tyre-dimensions/#2
I have just twigged your avatar.
Your site was very helpful, I have come across a few similar about sizing and widths but seem to confuse more than help, nowhere could I find that definitely told me that 47 was 1.75 especially when 1.50 is not 1 1/2.
My inside rim is 19.40 so I am good to get the 1.75s which are on order - so thank you for your help.
Glad it could help. The site started by publishing my own notes - that I use to help myself (can't memorize everything always). After a wise friend told me I should put that on-line, so I can use it wherever I go, and "perhaps someone else could use that".
It's still used that way: the way I would like to have things explained to me.

A few years later, I published the stuff that helped me keep the cycling site running, effectively making an IT website, done in a similar way (long, thorough, boring):
https://io.bikegremlin.com/And, finally, just for fun, a personal blog, with stuff & nonsense, which I don't really expect anyone to read, but it feels good writing it
https://blog.bikegremlin.com/