Sadly I know a lot about old French bicycles, since I have no life.
Sparting was a manufacturer of pushbikes and small motorcycles located in Rennes.
The earliest bicycle from them I ever came across was from 1922, but I assume they started earlier than that.
The newest ones I've seen are from the 1970s. I have no idea what happened to the company afterwards.
The example you shared with us is pretty certainly from the early 50s and very likely on 650b tyres.
It is imperative that any old French bike you buy is complete, otherwise you will end up in a sea of misery (guess how I know).
Not only are all threads metric, but also the stems, handlebars, etc., so nothing you can find in the UK today will fit.
This means you have to get everything sent from France and let me tell you, dealing with the French is tough to put it mildly.
Only in the Eighties the French bike manufacturers gradually adopted standard ISO bits.
To be quite frank, I'd leave it where it is and not look back.
If you are really interested in a vintage French 650b, try to find a better one to start with.
However, if you still decide to go for it, I shall avail you all the knowledge I have.