Eeek yeah, perhaps they were out of stock on 8's but the 6's have been labelled as 8's so when they are "out of stock" and then back in stock, it means they have been returned but not marked correctly so you're seeing them out of stock, then back in because people returned the 6's.
Okay, so my dress saga is almost resolved, but not quite.
The final order was delivered today around 11:30am (after my night shift), which means I've only had about 3.5 hours of sleep since yesterday morning... and I checked the size as soon as I opened it and it was a size 8

!
Then I put it on and realised they'd sent me the regular length, not the short length... which is what I had originally ordered in the first place and had returned on Monday because the short length was supposed to have come back in stock

.
So, after ordering 2 dresses in size 8 short, I ended up with a size 6 short (right length, but way too tight), a size 8 regular (a better fit, but too long), and a size 10 regular in a different colour (too big, and too long).
I called Coast to complain and the lady I spoke to was really nice. She immediately refunded the £4.99 delivery charge since it didn't arrive on time, and then she looked into what was going on with the incorrect sizes. She said that the stock room had one size 8 short in stock, but that it was likely the case that it was damaged, so they sent the other size(s) instead. She said that she could contact the stock room and check on the state of the dress, and get back to me, but that would take time, and it would still take at least 5 working days to arrive if it was ordered, so it may not arrive in time.
Because of this, she offered a compromise:
if I keep the long dress and get it altered, as long as I have proof of payment, they will refund the cost of the alteration

.
So, I agreed to that (they sent an email confirming the offer) and took the dress into an alterations place this afternoon (as I only have 8 days to get it done!) - they said they can do it by next Thursday... so it's finally looking like things will work out!
I know Coast have been having problems recently, with going into administration and closing stores, so I guess they aren't as on top of things as they used to be, but when I put in the first order last week, I never expected there to be this much drama! If their dresses weren't so nice and didn't fit so well (apart from the length), I wouldn't have bothered

.