The biggest headache is whether both the supply and the electric cable
line up with the replacement unit. I stuck with Triton for two units
because they did line up. When they changed the design I moved on but
had to strip off tiles and change the feed pipe channel.

The other thing to be sure of is that there is an isolation valve - a
friend of mine tells a wonderfull story about changing a shower without
being able to find an isolator anywhere - in the house or a toby in the
road. He had to do it live - got very, very wet and very, very cold
but he did succeed.

If yu're not into plumbing, electrics, tiling and a bit of chasing
then call in the plumber.

Rob
Rob