XL frames will always have a limited market as you’ve said.
Other things to note:
– You’re pretty much a classifieds only user – that often puts people off
– Not many second hand bikes sell over £1k – people usually don’t want complete builds with your spec and that have no warranty.
– You’re asking for more than 50% of the RRP for a bike that has had unknown use and as above, no comeback if it breaks on the first ride. Standard formula is 50% off for the first year and then 10% per year after that.
– You want collection or posting at their expense – that adds to the already high price
For high value bikes, you’re almost always much better off splitting so that people can buy the parts they want.
Or failing that, ebay on a zero fees weekend where it’ll sell for what it’s worth.