Are there any issues with replacing the 16" wheels on the estate with 17" wheels?

No

None at all, did it on my vRS Estate with no issues other than the ride being a little firmer but nothing to worry about.

Or 18's

Only if you don't fit lower-profile tyres, to retain a legal speedometer calibration (-0% .. +10% of actual road speed).

Thanks for that. I think these wheels will mean lower profile tyres as the aspect ratio is 45. Is that correct? Sorry not astute in terms of these round silver things. You can probably tell!

Wheels are audi S3 ones

225

aspect 45

offset 32

Thanks again

Thanks for that. I think these wheels will mean lower profile tyres as the aspect ratio is 45. Is that correct? Sorry not astute in terms of these round silver things. You can probably tell!

Wheels are audi S3 ones

225

aspect 45

offset 32

Thanks again

That tyre size is fine.

Thanks very much Eddy

My Octy RS combi is sitting on 18s without issues.