BAS Towers may need to have it's CU moved, with circuits extended using DIN rail terminal blocks.
Now - I know I said this:
//www.diynot.com/forums/viewtopic.php?p=165038#165038
but I'm sitting here thinking yes, it's unconventional, and yes it makes testing more awkward, but is there really any great merit in extending ring final line conductors with 2 terminals and 2 x 2.5mm² cables into the CU rather than putting both legs into one terminal and running a single 4mm² to the breaker?
I think that you (with your old thinking!) and I also crossed swords over this one in the past, but I agree with you (new thinking!) and Eric that there seems to be nothing intrinsically wrong with doing as you suggest. There would obviously be less scope for argument if, as Eric suggests, you used 6mm², rather than 4mm², cable - since (although one can stage some sort of argument by analogy with a 32A radial final) there is otherwise obviously the scopr for people to start fussing about the 'CSA reduction' from 2x2.5mm² to 4mm².
In fact, I inherited a situation like this in my house, and happily lived with it for several years. A 6mm² (well, imperial equivalent) cable which appeared to have originally been supplying a second cooker circuit in the (large) kitchen had been diverted into the (large) cellar and used as the start/finish points for a 2.5mm² (imperial equivalent) ring final circuit. As I say, I happily lived with that for a good few years, until I eventually treated the cellar to a sub-main and its own CU.
As you know, I do my best to play at Devil's Advocate, but I find it hard to come up with any 'sensible' objections that anyone could raise, particularly if you used 6mm² cable. You should, of course, label your CU appropriately, so that anyone coming across it knows what is going on, and knows where to find the ends of the ring for testing etc.
Kind Regards, John.