Well to give you an idea on the post office, a heater to send well packaged was £2.25, looking at the weight on the site with standard parcel it would still be at least £10 and that is not including me getting some bubblewrap etc to try and get it there altogether, I could write fragile all over it but it still would not guarantee getting there in one piece..
If you were able to collect at some point or get someone to collect I am more than willing to hold for you as long as at least a deposit or payment is put down (as done something like this before and it ended up having to be resold months later!).
There is also now a triangle small tank available with lid for £5