As above, the creda has had it, gotta confirm the size of the cable,but sure its a 10mm, was hoping to replace with a Mira?
Take the opportunity to get a proper power shower fitted - don't waste your money on another electric one.
Minimum 9.5kw or get a 10.5 if you can.
Mira Sport - had them before & very good, no need for power shower if you use one of them IME.
mira sport has multi positional fittings but is dear.. at work i fit triton t80 multifittings for water and sparks..ALWAYS ALWAYS get a proper spark in to test your electrics most of the failures.. FIRES.. SMOKE.. are because old or inappropriate wiring was used.. just because it worked fine last time is absolutely NO guarantee of what will happen in the future..
(IMPORTANT BITS HI LIGHTED IN CAPS.. BECAUSE THEY ARE REALLY REALLY IMPORTANT..)
I put a mira sport in hoping it would be decent, add promised by the plumber and electrician, but the flow rate is rubbish. Imo do EVERYTHING possible to get a standard shower or regret it. YMMV.
One aspect to check is existing water pressure, if not too good, they now do a pumped version, but I guess it may cost more.
Water pressure (and £) defines what you get, I remember years ago a combi boiler always takes ages to fill a bath, but the mains pressure was high and a mixer shower would take your skin off!