You need a registered VAT number, but IIRC it costs nothing. It is a cash and carry shop, so don't expect a glamourous place (although there are plenty of polite people to help). The benefits of membershiip.......you get to shop there, very cheap food and drink aswell, but if you just want a few chairs see if you can lend a card.
Surely its possible to refill the cushions if they become flat after use? As mine will only be getting occasional use I couldnt justify a higher price tag or the grief off the missus the higher price tag would bring