Not sure if this is still going to be useful to you but when my wife and I upgraded our tent this month I did a huge amount of research and uncovered the following:
Anteus 600 is exclusive to Go Outdoors, whereas the Avington 600 can be bought at a wider range of shops. The same photograph of the tent is shown against different names 'Anteus,' 'Avington,' (and even some other names) on various retail websites. (You can see the window reflections and creases are identical on the Anteus/Avington on the Vango site too. Only the name has been changed on the fabric! (I teach music in a school and one day a pupil didn't show up, hence my far too in depth knowledge into this stuff!!)
The dimensions are identical and the price is the same.
Key differences: the hydrostatic head on the Anteus is 3000 and the Avington is 4000. The side door on the Anteus is a single sheet, zipped in or secured open. This appears on the Avington along with a separate mesh sheet on the side door so you can have both doors open for breeze but 100% insect protection.
The avington is green and the anteus is blue.
Also, the universal Vango Carpet 260x360 almost fits the 380 x 260 floor space and it £20 cheaper than the tailored one.
I hope this helps. We've not been out in it yet, hoping to go next weekend but it's a bit wet!
I had this last year. It's exactly the same as the anteus.
I ended up buying mine online at WM Camping because they were by far the best price. Used it several times last year and it was fantastic! Loads of space for my family. 2 adults 2 kids. Would definitely recommend for families.
So happy I have seen this - I too was wondering which one to go for - Anteus or the Avington.
My local Go Outdoors has the Anteus pitched so will go look at that, see if my wife likes the size, then go for the Avington, purely becasue its cheaper.