Hey Aastii!
I imagine you will want to be taking shots of the cars going past if you're going to a Le Mans event, so for that reason I'd recommend you buy a superzoom. Something like this Nikon would be great
http://www.amazon.co.uk/Nikon-COOLP...3M56/ref=sr_1_2?ie=UTF8&qid=1362931629&sr=8-2 a 42x zoom is just about the biggest zoom you can get right now (Canon have a superzoom with 50x zoom but not only is it overkill it's also expensive).
Other makes to look at are Fuji, Panasonic, Olympus, Sony and Canon. They all make superzooms. I own a Nikon D3200 D-SLR and love it, and I also own a Fuji S4000 bridge/super zoom. The picture quality of the Fuji is OK but often photos come out a bit under-saturated. The zoom on it is good though (30x, but the Nikon I linked to has 42x). I used my Fuji at a BRM racing event in Bourne last October and was able to get some got good shots of the F1 cars as they went past. I would imagine the Nikon will also be fine for your F1 cars. Also owned a Panasonic superzoom in the past (DMC-FZ8, old model from about 2007), it was good - not sure what their newer superzoom cameras are like. They're probably also good.
You may want to go to a local photography store (too bad Jessops has gone bust, eh?) and try a few out - see which ones you like.
SD card wise, I think an 8GB SanDisk card like this will be fine
http://www.amazon.co.uk/Sandisk-30M...4?s=electronics&ie=UTF8&qid=1362931734&sr=1-4 each file from that Nikon will be about 5-10MB I reckon, so 8GB should be more than enough. I have an 8GB SD card for my Fuji S4000 and I've never come close to filling it, even when I've taken hundreds of photos on holidays.
Case wise, I always recommend LowePro so I'd say this would be good
http://www.amazon.co.uk/Lowepro-Sho...?s=electronics&ie=UTF8&qid=1362931968&sr=1-10
Whole thing comes to around £276 so it's within your £300 budget. That's all you will need.
Even if you don't go for the Nikon superzoom I'd still probably recommend that card and case.
Hope this helps.