So I am thoroughly confused....
What should a 2011 Plus 4 be running? Mine has I believe the original factory fitted tyres... which are avon 205/65 r15. When I look at a tyre company's website based on my reg it says they should be 195/65 r15. The handbook supplied is for a later car... it has 4 tyre sizes none of which is what is fitted...
It depends what rim width you are running. I believe that +4 rims are 5.5" - in which case the tyres should theoretically be 185s or 195s. If you have 6" rims then 205s would be ok, but would probably make the car feel pretty ponderous to drive. On a 5.5" rim they'd be a bit too much and I wouldn't recommend replacing with the same size.
If you have 5.5" rims, and you would like your car to feel more nimble and agile, then I would go to 185, or 195s if you prefer a more 'planted' feel. Either would cope perfectly with the power output of a +4.