A quick update - came home from work and replaced the oil temp sender with
the proper one - looked at it closely and it even said VDO on it even
though I bought it separately from the VDO gauge.  Removed about 600
millilitres of oil in the process and went for a drive around the City in
after work traffic.

Now I never got out on the open road so I couldn't really get going to
check on things too much but I can say that around town stopping and
starting in mid afternoon sunny weather I was running about 218 F with the
first stage of the fan kicking in and out.  Not a lot of consistent air
flow or sustained speed.  Oil pressure at idle was a little higher at 21
psi from 18/19 yesterday - not sure if it had anything to do with draining
the oil level down which in turn kept things a little cooler.

So now it seems I am a bit more in the ballpark when it comes to oil temp
and can start dialling things in a bit more to understand the operation of
my motor.  I think both suggestions made quite a difference.

Bruce