Gaz,
yup my tyres are for different jobs, and M+ are noted for being a swine to fit. Schwalbe makes lots of different tyres, all for different applications. I was just trying to point out that there is more to how easy a tyre will be to fit than its width alone as both types are exactly the same size.
Width is a factor (both on rims and frame clearance) but I'd be surprised if it makes any difference to fitting for the OP