Yep that was my thought, be fine on the fcu. I'll have a look tomorrow to see if I can extend the ring. But I'm not holding my breath.If it's in capping you might be able to get a second cable through but if not I believe it's perfectly OK to have the FCU on the existing single cable. It will still protect the single 2.5 T&E against overload.
Would have had it finished today but discovered a leaking waste pipe while.running the cable and that turned out to be a bigger job then expected.