I used the car the other day, first time in a couple of weeks. Car was pulling left for several miles and hot smell from O/S calliper.

Logic states that it was temporarily seized.

Car is always garaged, 77K miles.

Is it worth stripping or go straight for a new calliper, (I guess they are fairly reasonable?).

Pulling left would suggest binding NS brake, not offside. But it's worth pulling them both off, checking the sliding pins they are bolted to to make sure they are moving freely and pumping the pistons out slightly and pushing them back in. If it is the sliding pins, you may be able to free them off or it's new calliper carrier time. If replacing callipers it's probably best to replace as a pair so you don't get uneven braking.

Good point regarding both!

I will check it out later on.

Right brake was overheating and it pulled severely left.

My diagnosis was a seized R/H calliper that was slightly on to generate heat and the L/H only doing the braking. Maybe!

Was an nteresting dance braking with the car trailer on.....