Hello Thanoscy. I see nobody has been able to answer your question and I am afraid I cannot either.
When I was thinking about how to build my little raised pond, I did consider concrete, but only briefly. I thought, perhaps wrongly, that there were too many ifs and buts with concrete. Also, I have had experience with butyl in two previous gardens and was very happy with the result.
Living in Crete makes it a little easier for deliveries of goods from the U.K. When I bought my pond liner, underlay and pumps, they were delivered free of charge to Nomad International in Peterborough.
Nomad does not charge by weight, but by size.
Nomad have a fortnightly delivery to Crete, but of course they have to pass through Piraeus from where the ferries to Cyprus leave. It might be worth talking to them.
http://www.nomad-international.com/Or, Amazon sell pond liners. That could be another option.
Hope this helps.
Daisy