If the dealer is being co-operative and trying to solve it I'd let them get on with it before getting all arsy and quoting the SoGA at them which may mean they decide to just do what is required under it which is probably less than you are currently getting.

Only look into the SoGA if you reach an impass where they can't fix the car and won't do anything further to help you.

For the time being I'd just firmly but politely request them to ensure it is fixed and ask for a loan car whilst they are doing so.

I've got a vague memory that there were some software updates for the C70 due to the roof mechanism not switching off completely and draining the battery.

If your supplying Jaguar dealer can't solve it I'd press them to get it into a Volvo dealer (which they have probably got in the same dealer group) and check there isn't a technical service bulletin for it.

As alluded to above, the fault was obviously present at the time of purchase (they had to put a new battery in before you could drive it away) so the onus is on them to fix it.

Politely but firmly remind them that you'd like the problem solving and give them a chance to do so ... if they fail to do so or start to get recalcitrant, that's the time to get serious with them.