I've got some Coopers PET bottles, I had a beer in them conditioning for about 5months - came out perfectly fine.
I also use glass - I prefer glass personally, as I can use my steam steriliser to sterilise them, I am pretty sure the Coopers bottles would deform under steam.
I also had a word with the local pub, they were more than happy for me to take beer bottles off them - mind you I did work there some 20years ago, and some of the same hands are still there.
Pop into another local, or if you are on Facebook or similar, ask your friends if they will save you empties - you'd be surprised how many friends you have who will save you their empties in return for a few samples :grin:
Failing that, you could buy glass ones from a manufacturer, I did when I had no other option - I paid about £28 for 60bottles direct from the manufacturer, each one came with a crown cap as well, and there was £7 in that price which was delivery.
I used these:
http://www.jbconline.co.uk/
http://www.jbconline.co.uk/glass-bottles/beer-bottles
These specifically
http://www.jbconline.co.uk/glass-bottle ... -with-caps, however they had a less than half price sale on them at the time, which is why I bought them.
They have these on offer:
http://www.jbconline.co.uk/sale-30-off/ ... -with-caps
330ml I think is like a Budweiser bottle, but you get 100 for £26
There are of course other glass suppliers, and you might have a local one that you could collect from, hence saving you postage.