I really need to make a large article/post on selling on ebay. I've sold on ebay for quite a while (over 500 rep), and there are many things that 40k players don't realize:
1. Half is normal. That's right, if your item is used and out of the box, it's not surprising at all to only get half the retail value. By my count your items have about a 200 pound value 'retail'. So 100 pounds is around what you're probably going to get in most cases. That doesn't only go for 40k, but virtually anything bought and sold on ebay. You can definitely get more than half, with a nice paint job and close up pictures...which leads us to...
2. If they're well painted, make sure you show close ups, and multiple angles. Saying something is 'pro-painted' is a lofty claim. You're basically saying that your items are better painted than 95% of all the painted 40k items on ebay. You're going to have to show close ups to back up those claims.
3. You will almost never get more than full retail value, no matter how well it's painted. There are very few people who can make money painting miniatures, and most of the time they still have to be a distributor, so they can get the items at cost. Of all the 40k items I've sold, I only remember it happening once with me, and it was for a very well converted dread with auto-cannon arms. On that note...
4. Show close up pictures for conversions. Even then, most conversions aren't going to sell for much unless it's very well done, crafted with a lot of skill, or if it involves hard to get bits. With the auto-cannon dread, it's because I needed to attach 4 separate auto-cannons to the model, which most people don't have easy access to. I also like to think I did a fine job putting it together.
5. You'll always get more $ if you break the set into smaller lots, usually of one unit each. Very few people are looking for all the items you have listed there. Most people only want half of what you're offering (and that goes for any large lot), so they're only willing to pay good money for the items in the lot they want. The items they don't want, they'll only be willing to pay less than 1/2 price. So if you want the most money, break that lot down.
6. There is always a massive 'glut' of models on ebay that come from the starter sets. In this case, it's assault on black reach. I just did a quick check, and I found several sellers on ebay selling the entire Ork half of that set, new and on sprue, for 20-25 pounds. Regardless of the fact they're painted, that's probably the most you'll get for them. Most Ork players simply don't need any more warbosses, deffkoptas, or slugga boyz.
7. Finally, even if the items you're selling are in relatively good demand, there are a LOT of warhammer items for sale online, because many people start the hobby, and then for whatever reason, stop playing. Also, a lot of people selling them on ebay are retailers, looking to sell old stock at high discounts. In order to compete well, you either need to repost the items several times and hope you get lucky, post them for dirt cheap, or do a really good job presenting the models, with very clear and close up pictures.
All things considered, I estimate the value of what you have there to be around, at most, 100 pounds. Sorry, but that's the sad truth of the matter. Good luck!
The first casualty of war is neither innocence nor truth.
The first casualty of war is always subtlety.