Please answer asap when u buy a car from a garage legally do they have 6months warenty?

[raverbean]

i brought my car back in november within a week engine came on they so called fixed it. now its back to them again (1 march) theres water in my oil and engine light is back on. i thought it might b head gaskit. but now there refusing to pay anything as its over it warrenty. ? (sorry bout spelling) what can i do? x