oxford humpback tank bag question

I just bought the oxford humpback tank bag. It came with magnet base. As far as I understood, one can also use it as a tail bag with a different base which I bought separately. IT DOESN'T FIT TOGETHER! Are there two different types of the bag? Is one of them the 3 in 1 and the other just a tank bag? They look exactly the same. So peed off! Can't return cos I bought it on ebay. I bought it cos I wanted to have the option to have it on the tank or on the tail. No can do

This is what I bought (bag): http://www.ebay.co.uk/itm/1907088262...#ht_500wt_1413

This is the extra base I bought:http://www.ebay.co.uk/itm/2710233900...ht_2646wt_1180

This is what I thought I was getting:http://www.oxprod.com/index.php?pg=3...&id=16&pid=2&p

Is it the teeth in the joining zip that are different?
I had a similal experience a while back.
I think Oxford changed the zip pattern at some time, meaning that not all Oxford stuff zips together.

BAST**DS!!!!

The way the zips are lined, you couldn't zip them together as they are both facing down if that makes sense. Not to mention there is no zip pull on the new base. There is obviously no zip pull on the bag as the pull is on the magnetic base. So one would expect to find a zip pull on the tail base but nope! I tried calling them yesterday but there was no one to help. I'll try again today. What a waste of money! I'm so angry!