lock problems on XKR

[Qcarchoo]

After a few weeks of not driving my XKR I couldn't unlock it on the key fob and it appears that the battery is flat, as the red alarm light next to the gear lever isn't working. I tried the keys in the lock but it is seized. Does anyone know if there is a back up battery on the alarm (I'm reluctant to open the boot to charge the battery if it's going to trigger it), or if there is any other (sensible) way of gaining entry.Thanks in advance.