Throttle response problem

Dear all. I am an avid reader of this forum and have recently purchased a petrol vrs 2009 model.

Up until yesterday all was well, but yesterday afternoon and this morning a weird problem has started. It's difficult to explain fully, but I'll try. When i apply slight throttle in 1st gear from idle the revs shoot up in controllable to around 2500 rpm then fall down slowly when I take my foot off the throttle. However the second time I apply the throttle gently it revs up to around 1200 ( which is normal). It doesn't matter how gently I apply the throttle from idle it shoots up to 2500. If I try and then release the clutch the revs fall sharply and the car almost stalls. this is becoming problematic as I do about of stop start city traffic.

Prior to yesterday this didn't happen at all. I don't think my driving style has changed recently so I'm wondering what it could be. has any one else experienced anything similar?

Any help from you clever people out there would be greatly appreciated. Do u think it's something easily solvable, or will I need to book it into a garage?