Shower mixer installation

Hi, hoping to get some advice please on installing a new shower mixer for my Mum following a flooded bathroom.

I have managed to remove the existing old mixer (Aqualisa) which was probably installed in the 70s or 80s. The separate hot and cold supplies are 22mm, although it may be 3/4 inch......not sure how to check?

I have bought a new mixer (Triton) which requires a 15mm feed......l assume I need to fit a reducer 22cm to 15mm?......does it matter where I fit this?......I am planning to cut the existing 22mm pipe in the hall cupboard just before it feeds through to the bathroom.....presumably the later the better?

Final question, the existing shower feeds are 165mm apart. The new shower needs 150mm. Seems like 150mm is the standard now, so presumably I will need to drill out the goes in the wall so I can bend the pipes in a bit to reduce the gap to 150mm?

Any advice very greatly received!

Triton are ****e, take it back and get an Aqualisa

You're correct that you'll need to adjust the pipe centres. I'd fit a 22mm isolation valve to each supply, with 22×15 reducer in one end. It won't make too much difference exactly where you do this - within a metre will be fine. They're designed to be fed with 15mm all the way from the supply, after all

What heating system do you have ap77 pressurised or gravity
Regards david

Many thanks guys for taking the time to reply.

My Mum has a hot water cylinder in the airing cupboard and a cold tank in the loft so believe this is a gravity system.

Is it possible to buy reducers with isolators built in?

Stick with the Aqualisa. 22mm feed v 15mm feed? Ask Aqualisa why they use 22mm and also why they prefer copper pipe. What is the flow rate of the Triton and does it compare with the Aqualisa. Fitted my first one 30 yrs ago after a trade show and was sold on the flow rate. Still have original sales bumf quoting "400mm head will give in excess of 1 1/4 galls/min and with 1m head, 2 gall/min.