Not really what i wanted to hear, but if im honest i did expect it.
So, assuming i have to take the cheapest possible route (after calling a proper sparky) can i simply use the spare RCD protected slot for the garage and use a higher rated breaker to cope with all the garage equipment?
Dont think i can afford to get this completely fixed, it works as it is now, although the tripping breaker is obviously very annoying and inconvenient!