So, after replacing the cracked coolant cap I have with a brand new one, I'm still noticing coolant squirting out from the cap despite it being tightly secured. I know this is a big sign of the head gasket being blown, but I'm not noticing any other symptoms, as in the car is running extremely smooth. I haven't had chance to check the oil yet, but will be checking it very soon (next day or two). So I have 2 questions, how much is it going to cost to get it fixed (I'm not getting rid of the car), and how long would I have with it in its current state, since I drive A LOT to get to work.

have you used a Hydrocarbon test kit (Amazon about £15) to test for exhaust gases in the coolant ?

It would at least prove one way or another as to why the coolant system is being over pressurised.

58 minutes ago, unofix said:

have you used a Hydrocarbon test kit (Amazon about £15) to test for exhaust gases in the coolant ?

It would at least prove one way or another as to why the coolant system is being over pressurised.

I haven't, I haven't got the money for it until payday. But as soon as I can, il be ordering one

You COULD buy a bottle of Holts Radweld from Halfords, about a fiver, and try that. I've got a Subaru Impreza, they use laminated head gaskets with graphite which starts to leach out around 100k miles. Subaru's official 'fix' was a bottle of 'coolant conditioner' which turns out to be Holts Radweld. I've had it running in my Impreza about 3 years now and I've only had to apply more Radweld once. Much cheaper than new hg skimming head, etc, on a 20+ year old banger. 

13 hours ago, Connor Wetton said:

I haven't, I haven't got the money for it until payday. But as soon as I can, il be ordering one

If you have a friendly local garage, they may do it for free.  Only takes a couple of minutes.