Will be doing a couple of ground floor bathrooms, one a wet room,one a shower tray at floor level, but before I go any further I need to know what provision I need for the drains, this is a property under going a lot of extension work.
110 plastic undergrond drain pipework has been left exposed below floor level outside for me to connect wastes from both one shower tray and one wet room tray, question is can I just tee ino the 110 with a 40m/m solvent weld boss and run back to the tray, do I need a rodding or inspection point? which would not that easy to conceal.

You dont need an inspection chamber and a rodding point would be conspicuous, a bossed in join would be fine. Are you fitting a trap?

Yeah there will be the usual trap on the trays. Thanks