Well, finally got ACE problem sorted! Took it to Maltings offroad near Doncaster. They removed the ACE system completely and reverted back to standard with new parts. No more Red light and 'bong bong' and no effect on ride either. Cost £1100.00 + £40.00 for Mot.
However, on driving home, after 40 miles, now got 'transmission fault' warning and park brake fault warning and Yellow brake shoe light on! I am mortified to say the least and my son will probably take a sledge hammer to the biggest moneypit this side of HS2!!!
Hopefully, it might be just something to do with the removal/replacement of parts for ACE system?

Just this morning checked battery after been parked over night. With engine off, meter read 12.13v and with engine running it read 12.70v.
Could this be causing the warnings?

thats a low reading for battery with engine running

cant says if it is fault cause, but cant be good either.
get that checked out first. if it is battery shot or altenator is not putting out enough.

check rear brakes and handbrake shoes and cables.. ...

tranny fault... god knows ... hopefully not terminal

If the ace pump has been removed I think it requires a different alternator.
So maybe duff one fitted