Can't find it anywhere ???

Any Website, Store etc ???

I don't know if this company is actually in the UK or not, but shipping to the UK is free.
http://www.vistahair.co.uk/products-page/

There aren't that many product details, so you may need to contact them directly to find out if any of their tape rolls or contour tapes are 3 mil.

The only UK company I know of that sells it is Steiner Hair:

http://steinerhairunits.com/product.php?id_product=68

on a side note, where can you buy ORWG without paying cp's high shipping cost.

I get mine on ebay.co.uk.
They have it on ebay.com too.