welcome to the forum!
im not too big on motorsport photography as im yet to buy/afford a lens that suits. however you really need to practice your panning technique so get down to somewhere like castle combe or brands and get practicing, im not sure how good the spactating is camera wise but get in on it

hopefully they might come up with some rules to make formula 1 more exciting between now and next year cuz at the moment any historic/club racing or bike racing kicks its ass for interest!
im off to the rally GB with my certified rally rut photography friend next friday, i hope she enjoys herself and doesnt drop my camera in the mud!
i went to the gold cup at oulton park last weekend but with a 50mm lens it was a futile opertunity trying to photograph the cars moving