My tyres are getting close to needing to be replaced. Current my 215/50/17 tyres are all 94 W. Would it matter if one axle was replace with 98 W and if so which axle would it be best to mount them on?

98 is a better load rating than 94, so there won't b any safety or performance concerns.

7 minutes ago, JR RS said:

98 is a better load rating than 94, so there won't b any safety or performance concerns.

Would there be any issues, as I assume they would have stiffer side walls, on handling?

I doubt you would notice any difference. I have used XL (98) winter tyres on the front axle and felt no difference in terms of handling/ sidewalll stiffness.

On another car I had previously replaced the skinny spacesaver spare with a full sized wheel and a spare tyre that happened to be XL rated - and when used, felt no difference to the standard load tyre it replaced for a long journey home

Edited 17 October, 202517 Oct by Shuggyboatsuperb
Finished

The main thing is to get decent tyres.

There's various trade-offs. Price, longevity, dry grip, wet grip, aquaplaning resistance, rolling resistance. Getting the best compromise on those is more important than the load rating.

Tyre Reviews has loads of info on tyres.

Another thing is where and how you get them fitted. The vast majority of tyre place, just paint a bit of stuff on the rims and fit the tyres. I've found that about 1 in 4 tyres will have an irritating leak as a result, losing 1 or 2 or 3 psi per week.

Finding somewhere that cleans the rim with a wire brush / file when they fit tyres is worth it, even if you pay a few pounds more.