Think regular coffee and cake stops. You won't need a camelbak but a portable potty might be a good idea!
Suspect I'll be "over-equipped" and end up not using half of what I take (that's assuming it all fits on the bike), but it's been great fun finding all the stuff and I've not spent out too much.
Optimate cigar adaptor lead (Ally Pally show ) £8
Phone charger (EBay) £1.65
Rechargeable Batt cigar adaptor charger (7dayshop) £3.69
Wind-up usb charger (Maplin) £5.99 (may leave behind)
Head torch (Lidl) £2.99
New helmet - long overdue (Infinity) £40 (bargain)
New bike sunglasses (Bikesafe show) £15
lightweight leather gloves with kevlar lining (EBay) £12.99
Gelert camelbak (Amazon) £7.95 (but £2 after credit mistake)
Dry bag (Aldi) £5.99
Stop'N'Go puncture repair kit (M&P) £4.99 (if it arrives next week as promised)
Crampbuster (M&P) £5
Compass (Asda) £3
Osram Nightbreakers (EBay) £13.95
Tutoro oiler £14.99
Sheepskin (Ikea) £20 (although we already had this sitting about unused)
Actually it does rather add up when you list it all out - ooops.