Sorry to hear of your loss, gleno1.
Some advice
Islington and Camden Cemetery is huge. It's the largest cemetery in London. There are a number of different chapels within it and they all seem to be miles from the road. Your train gets in at 10am, if you get the tube immediately, you'll be at East Finchley by 10:30-odd. (Only get a tube that's going to Barnet or Mill Hill East) It's a bit more than 1km to the gate of the cemetery and could easily be the same distance once you're inside.
When you get out at East Finchley, there's a cab office immediately opposite. They'll know the place inside out. You'd even have time for a quick cuppa in the cafe next door before you go.
Alternatively, I live within five minutes and would be more than happy to take you up there. Dunno if the AB's rules allow that, or how we could make contact, but there has to be a way.