Mira 723 mixer shower service kits

I am B&B owner and about to service 3 acient Mira723 mixer showers using genuine Mira service kts supplied by the Shower doctor.com.
I am pretty handy re diy but I need to get the service right 1st time as the rooms/showers cannot be out of use if I make a cock up.
The instructions/ expanded diagram supplied look ok but has anyone had any experience of servicing these showers using the kits and are there any tricky issues that it would be usefull to know about in advance before I take em apart.

The instructions that come with the service kit are pretty idiot proof. Just lay out the o rings and washers on the printed template and cut off the old ones. Do it methodically and you'll be fine. please remeber to make sure you get all the old plastic washers out especially the one behind the main cover.