I've fitted a few modern close coupled WC in place of old low level systems and they always leave a space between the cistern and wall that I have to fill with a spacer of some sort. The base of the WC is hard against the vertical waste outlet, so it cannot go further back. Anyone know of a suitable WC system that willl fit better. Just had a thought maybe I should choose one with a cut away6 base so the whole thing would move back closer to the outlet and therefore the wall? Any ideas?
Assuming that your waste discharges to a connection at floor level try using a "space saver" 90 degree pan connector. Screwfix dont list one, but it looks like a letter p from the side, the rim of the inlet is in line with the vertical leg. Some plumbers merchants refer to them as Q-traps. Failing that you will need to reformat the branch connection to the stack.