Hi Maty, if the rust is surface rust only, no problem, but if it's pitted, don't touch it! Also check the inside thoroughly. I don't think Chambers would supply you with anything dodgy, but as Rochdale says, you're dealing with high-pressure air, and you could do yourself, (or some-one else,) some serious damage. I think it's the kind of job where you need to know exactly what you are doing before you attempt it. Do you belong to a club where anyone could give you some "on the job" advice? (Oh!...Err!... Missus!)
The ox is slow, but the earth is patient.