Unfortunately the full size models are not as an attractive an item as a wearable costume, they serve no functional purpose other than to stand static on display and look decent. The Death Trooper isn't the most popular of characters, so he won't be a premium (yet), but may prove more popular over time if they appear in other yet to be released films.
I think a Darth Maul (Pepsi promo piece and a very good model), which despite being prequel is much more loved as a character, sold recently on eBay for c£450, though I can't find it in sold listings now to check...
Jawa's that are fan made (again more popular as they are original trilogy) are selling around £150... R2 units can start around £500 and up then depending on motors and other electronics.
So, I'd GUESS it would be in the £300 region, maybe a touch more to the right person... its certainly a lot of bang for your buck and could see a shop sticking a much bigger price on it, but that both adds a point of interest to the shop itself as well as possibly generating a decent income if it sells.
In contrast, the wearable helmet from Anovos retails at just under £500 alone, building a wearable uniform to go with that is likely to cost you at least that again, maybe more, but that would be wearable as well as displayable.