Craig,
I think I can speak with some authority on this having just sold my late fathers 1934 Super Sports.My advice would be to persue contacting the Three Wheeler Club chairman Brian Clutterbuck. If you send me an e.mail off forum I'll happily supply you with his contact details.
Jayandt@gmail.com
Brian was a friend of my fathers and was able to advise us on estimates of value and where to dispose of his trike. We were a little anxious about using Ebay but it proved a very successful way to market the car and the listing fees are in the tens of pounds rather than thousands in commission an auction house or dealer would ask for to dispose of the car.
If you use Ebay ensure that you stipulate the sale will not be completed until you have cleared funds, and you can't really go wrong. Again if you contact me I'm happy to pass on any further advise you need.
It will finally end up as a balance between how much effort you want to put in to the sale. Best of luck on whichever route you go for.
Regards Jason