Hello Sam,
Potential buyers will search all the sites you have mentioned.
You are of course very welcome to post it on here and I would suggest you include as much detail as possible, together with a couple of photos, and the price.
Advertising on forums? Maybe too much of a generalisation, but forum members are mainly owners rather than potential owners, but worth a try.
Have you tried EBay? As with all internet adverts, you are at the mercy of time wasters, but…
WBAC will give you a bottom line sale price, and strangely I was talking to someone this morning who is about to use Motorway. They will give you a basic price, then put your car on a one day auction. You will then receive the highest bid, but you not obligated to accept it. Not sure (please check) but it might be free to list it.
Please let us know whether you intend to advertise it on here or not.
Regards,
Gareth.