Welcome along
In terms of valuation the Last 17 figures you have there are worth a fair bit of. Prices are fluctuating, but the R2 with popup saber, Luke Stormtrooper can get upto £300, the Han in Carbonite £150 - you might want to match the Luke to one of the blasters you have on a standard stormtrooper there - better value to sell a complete Luke than a common stormtrooper. The Imperial Gunner - not sure what he goes for these days, but £100+ for sure.
The Han and Leia first 12 figures are worth a bit - Han maybe £50ish, but as the Leia is complete with cape and blaster £100+ (the value is in the blaster and cape)
The Blue Snaggle is probably the big ticket item you have there - £500+ easily
The other figures are pretty common - maybe the Imperial Commander slightly less so - so prices are probably around £20-£40ish.
So overall, yes, a nice little collection with a few top end figures - The Snaggle, R2 & Luke Stormtrooper being the big ticket items.
If you are looking to sell, you will get more selling individually on here or Evilbay or the like, but also chances are you will be left holding a few troopers.
There are auction houses like Vectis that can shift collections - or you can try to sell as a bulk lot - although you'll most likely get lower offers as it tends to be dealers that by bulk and generally they look for 3x their costs.
One other option is to find a local comic book/vintage toys store and see if they will sell on your behalf (for a cut most likely).
good luck