maoned about. First question is - is it worth replacing - in the last
10 years have electric showers got better.

They are better, but probably won't be a straight swap, unless it happened
to be wired in 10mm cable, which is unlikely for a 10 year old one. Most
showers from this period use 6mm cable, which probably won't do for a
typical modern shower.

However, if there are bath taps nearby, it would be far superior to install
a power shower instead. These use the hot and cold supplies and pump them to
give much better water flow. They don't attempt to heat the water
themselves. Exactly what form of shower and repiping is required will depend
on your current water supplies and whether they are mains or gravity etc.
The flow rate of such a shower will be many times that of a puny electric
nightmare.

Christian.