...there's an online yahoo group devoted to SBDU Raleigh bikes where you can advertise it for sale for free to an audience that is interested in those bikes specifically. You'd need to join the group to post there, but it's not difficult to join. I would disagree that a bike from Ilkeston built with a Raleigh "professional 531" frame set is lower on the food chain. There are people who just don't especially like the ride feel of some of the newer frame tubing offerings from TI Raleigh. Some relatively knowledgeable people there ought to also be able to offer opinions on current value. Some one there might even want to buy it.
Anyway, look here for that SBDU group:
Welcome to the Yahoo Group "TI Raleigh SBDU RACING BIKES"This is for and about the racing bicycles built by Raleigh's Specialist Bicycle Development Unit (SBDU) at Ilkeston, Derbyshire, England from 1974-1986 under the direction of Gerald O'Donovan. Widely regarded as the acme of custom English framebuilding, design and and development, the SBDU built the frames for the famous TI Raleigh Racing Team including the one and only British-built winner of the Tour de France (1980) and pioneered the use of Reynolds 753.