For lighting charcoal I use whatever gas torch I have nearest to hand.
A quick blast of hand-held propane lights anything in a minute, then
leave it for 20 minutes to burn through.

Or if you're in a hurry I use the gas welding set. Pure oxygen (gas,
I'm not George Goble!) will burn charcoal to cookable grey in a couple
of minutes.

Faffing around installing a burner beneath things sounds like a lot
of effort.

I agree but considering this is a big (very BIG) BBQ it's worth it. To be
able to switch on a gas burner to get things going will be brilliant,
especially when the charcoal dies - just reload, switch on and 10 mins later
cook again.

So faffing yes but it's what I need so to me it makes sense.

I currently use a gas poker on a smaller BBQ and it works very well.

As for using a hand held torch... no thanks. This will be in a semi public
area so that would be a no-no, especially oxy-acet!