Just a thought, have you looked at the tyre pressure plate on the car? If Audi supply a 16 inch wheel as standard  for the A1 the appropriate tyre size will be on there. I suspect it will only be for M&S tyres.

Suggest 215/50r16 are probably the best fit.

As a previous poster said, check the offset so it clears the brake callipers. If wheels are from a similar VW group car then they will probably be ok. You can buy spacers but it's not ideal.

I'm not sure where you have looked on the web, but if you check out www.willtheyfit.com it gives you diagrams of offset, poke, inset, speedo error, rolling radius & more for different wheel sizes. The way it works is by you telling them what you have fitted now and then you input all the sizes your considering. It will show you how the different sizes of wheel will sit on the car, the impact on the speedo readings etc, etc, etc.

cheers i have done this on this site i was just wondering what other a1 owners are useing (tyre size ) 

Mmmm, I cant help with that I'm afraid, but maybe a1 owners will reply to your message.

thanks to everyone that has tried to help me on this post i will now go to the larger group of audi a1 owners and aske them for some more info cheers