For the last couple of days when I've pressed the keyfob twice to lock my ST the locks are clicking away and the doors are definitely locking but... the indicators aren't flashing at all which makes me think the double locking isn't coming on. Has anyone any suggestions on what might have happenned or what could solve it please?

To see if the double lock has worked chris sit in the car an double lock it u shouldnt be able to get out the car

Unlikely but is there any chance the bulbs need changing?

No the bulbs are fine as indicators, it's just when locking the car they're not coming on.

Could be a relay Chris

theres a sensor thinking it's open... is your interior light on when driving? like theres a door open.

if not then it could be the Bonnet one.

also try locking the car from outside with double lock with key.

turn key all the way to unlock then all the way back to lock!