All done now! We found a local toy shop where they had 2 boxes of them on a regular shelf away from the tills. It took around 15 mins for us to find the remaining 9 i needed.
Also i thought i may point out, when i detected one i already had, the next one back was the same too, ie. i found a ninja then the 4 behind it in the same row were all ninjas! They seem to be packed in rows of the same minifig. I also found 3 zombies all next to eachother too. Weird as i thought it was the same selection per box, but randomly placed in the box.
Oh well, now i have the full set!! Now i will buy another full set but leave them sealed this time so more valuable in the future