Some feedback on how it all went:
Before: 60A cutout. Dual tariff meter, 2 old Wylex wired fused CU's (one with a comedy home-made wooden backbox), electromechanical time clock feeding 3rd (comedy wired) CU for off-peak, Henley block and jumble of incomer wires etc. 2 Different comedy backboards, hanging off wall at comedy angle.
After: New 100A cutout. Wylex 12 way, split load CU (from Screwfix, incl 10 free double sockets - bargain!). Minimal install whilst converting an old chapel, CU on wall, 2 double sockets abutting it. New single traiff digimeter (smaller than a double socket).
Arrangements: Start by calling my supplier, explain what's wanted, they send letter with (wrong) number for EDF. Call EDF, explain what's wanted, they send quote. Pay quote for =A3323 (ouch). Arrange their surveyeor to visit. 5 minutes on site, no problems, also agrees reduction in charges to =A3240 - and specifies 25sqmm tails, 16sqmm main bond,10sqmm secondary bond. Letter from EDF detailing what I have to do (install new CU, arrange supplier to reconnect meter). Call to EDF to set this in motion.Call from EDF to arrange date. I call supplier to arrange same-day reconnect.
On site: EDF have giggle at old installation. Set up new backboard, mount new cut-out, snip through live incomers (nice demo of good live-cable working practices) and reconnect to new cut out. Fuse left with me to await meter company. (They also offer to reconnect old meter, but I pass on this).
Meter company engineer turns up. Tells me meter swap is scheduled, not reconnect - but says he will do it anyway. All connected up. Dead. Whoops - engineer still has fuse in hand- had forgotten to insert it! Fuse inserted - still dead. Whip off CU cover - one of the tails has pulled out! Major whoops - my fault - I hadn't appreciated that meter tails give quite a bit - but only when tightened down really hard! Reconnected - all good. Uses plug in polarity tester. I make up a small offcut of oak for his baby-gate at home. Everyone happy.
I finally test RCD and check earth loop impedance on new installation.
None of the engineers looked at CU test certifcate (download from IEE website, borrow mate's 16th ed. tester - thanks Ben, and very rare occasion to actually sign something using letters after my name) - though installation looked "professional" (used to be electronics engineer) - er - apart from the comedy pull-out meter tail - which is a pretty embarassing mistake to make.
Overall - it's the usual story of clueless phone-wallers and very capable engineers on the ground. I may have a chat with EDF about that =A3240 charge - the engineers only needed to spent 30 minutes on site.