the high/low has blown. I've removed the horn and washer bottle, and absolutely cannot get the connector off the back of the bulb. I can only get my left hand in there and just can't squeeze hard enough. So I've tried to remove the whole h/light assembly. I've taken the two top bolts off, it's still stuck. I've removed the wheel and liner, and just can't see the extra bolt that must be holding it.

I've got the factory manual but it's of no use here.

Any suggestions much appreciated.

You won't be able to take the headlight out unless you remove the front bumper as there is 2 bolts at the bottom of the headlight hidden behind the bumper.
These connectors can sometimes be a pain to get off but you just have to try and wiggle it off slowly, does take some time but it should just pop off.
Worse case is to chop off the connector so you can remove the bulb and get another one from a auto shop and solder it back on.

Done. What a PITA

The problem was that no amount of squeezing would convince the connector that it should let go. So I had to take off the wheel, the fender lining, the bolts holding the RHS of the front bumper, the grille, and the wind deflector to the right of the radiator. Then I could bend the bumper and get the headlight out. It's all good now but the whole job took me about 4 hrs. I changed a headlight bulb in our pajero the other day in about one minute.

The problem was that no amount of squeezing would convince the connector that it should let go. So I had to take off the wheel, the fender lining, the bolts holding the RHS of the front bumper, the grille, and the wind deflector to the right of the radiator. Then I could bend the bumper and get the headlight out. It's all good now but the whole job took me about 4 hrs. I changed a headlight bulb in our pajero the other day in about one minute.

They got the design of under bonnet components seriously wrong with the TL re space to change the bulbs. I only managed to change one when I had my TL and it took a long time... I gave up on the passenger side and let the dealer do it, who told me they removed the fuse box to get access.

I 100% agree.