From memory the 402c is the important bit as the R just means right hand orientation when fitted. We'll that is how I read it a few months back.
To get into the loo is easy as I found out when I did a descale with Killrock. If you slide out the flat flap that covers the big hole then you use this like a spanner blade to unscrew the seal assembly. One you have done this is all is readily accessible.

Colin

https://www.leisureshopdirect.com/water/...and-spare-parts

As for a bloke who has the ability to fix it we know and trust one fella called Neil but he does live in Lincolnshire.

Randa