Unless it's an oddball, no number on the bottom bracket would pretty much rule out an Ilkeston or Worksop frame.
The other common location for a serial number is the back of the seat tube at the top.
The colour scheme was used on just about the whole range of bikes from the cheapest to the most expensive, probably better to look for other signs of quality such as Campagnolo drop outs.
What about the steerer tube? Always worth checking there although without a serial on the frame you'd never know if the fork belonged to that particular frame.
Gorgeous frame bedraggled, looking forward to seeing it built up. I also have one of those Raleigh jerseys except mine is a Ralpar piece, not an Admiral. £100 you say? Hmm...
TVT 92 Carbone / 8sp Dura Ace 7402
1980 531sl Stan Pike TT / Super Record
1991 Raleigh Royal 531st
Battaglin Carrera SL / Suntour Superbe Pro
Duell Professional SLX
Merckx Corsa Extra / Dura ace 7402