Thanks

Thanks for that exactly the response I wanted so I'm going to go for the 17 inch
wont have to adjust suspension or anything technical cause I'm a useless mechanic

The 2006 R50 came with 15" or 16", with an option for the 17".  You can 'squeeze' in 18", but anything larger would have clearance issues. 

Other considerations include:

stress on the hubs / bearings & suspension - the MINI was not engineered for larger wheels
significant increase in unsprung weight - will dampen the performance of your MINI

Hope this helps.
Ken

ride gets awfully harsh with 20" wheels and handling suffers  18" or smaller is better in my experience.

mini vs. MINI = small classic vs. BIG BMW.

While there are plenty of MINI owners on here, this forum serves mainly mini owners and it might be a while until a MINI owner offers their opinion to your question.  

There are forums oriented towards the BMW MINI where the response time would be shorter, such as North American Motoring.  Good luck.

Hi Alex don't quite understand your post
was asking advise on putting larger rims on a 2006 Mini Cooper R50
why you say not on mini forum
but thanks for your child like humour 
thought was was a legitimate question

I've got a nice selection of 10" wheels you could try and fit.

More sensibly, you're much more likely to get a serious answer on a forum that is about Binis, this is a predominantly Mini forum.

thinking about some new rims for my 2006 Mini Cooper R50
any advise appreciated 
fancy 20 inch ?