Just to jump into this thread. I'm having the same issues.
My car is in for service and MOT this week at the main dealer, so I thought I'd query how much it'd be for them to do it whilst they were already working on it.
I nearly fell off my chair:
- £300 for diagnosis as they can't be sure that this is the issue. Fair enough that they don't know for sure, but I didn't want that doing and they refuse to replace without diagnostics. Plus this is the cheapest way to rule out other faults.
- If it is the Telematics battery, they estimate 4 hours work, so approx £1,000 for parts and labour!
I'll pop to their parts department whilst I'm there and do it myself at home.