Doubt you'll get anywhere near those figures tbh I'd say stick an add in for 2500 and take it from there. While I don't doubt the van is nice, the mods carried out may not be to everyone's taste, but it only takes one person to fall in love with it to take it away.
------------- Who needs travel agents,we have our static
If you want a quick sale put it on ebay, does it have a service history of annual services & damp checks? If not & it has been modified as you point out put it on for £2k reserve & go from there, good description & plenty of pics of course. Do it asap as its still just buying season, leave it a few wks & demand will drop with buyers wanting bargains.