'99 UK LX

The remote function of my ignition key has gradually been getting
weaker despite replacing the batteries twice. It now hardly works
at all. If I remove, then replace the battery it sometimes works
for 1 or 2 cycles. I'm guessing the fob has died.
Replacement at a dealer is an expensive option so I've found that
they are sometimes available on eBay.
If I buy a 2nd hand one I understand that I need to match it to
the car with respect to both the immobiliser and the remote
function. The physical part of the key is not a problem, I will
just swap it over.
The immobiliser part is also not a problem, I have done it before
using 2 other pre-programmed keys.
Is it correct that to program the remote function I only need to
turn the ignition on/off 4 times until the "door open-lights on"
warning bongs, then press the door open button? I have already
done this with the faulty fob in the forlorn hope of a miracle
cure, and although it didn't fix the problem the procedure seemed
valid.
Has anyone successfully tried this?

TIA

Chris