Hi Massey (I assume that's what your id refers to!)
Everyones opinion is different, based on their experiences.
After over 40 years working with big lead acids, here's my tuppenceworth:
1. Only consider 2V cells
2. Get the right size bearig in mind that they should last you for 10 years - plan for 5 years at least.
3. For a small holiday house maybe 300Ah (24v) will do, for a 4 bed permanent dwelling then 1000Ah is better.
(rule of thumb - don't discharge more than 20% each day and they will last 'forever')
4. Used batteries aren't necessarily bad. You need to know the history and buy from a reputable seller. There's some useless old rubbish about and some really good servicable stuff.
5. If you want best value, buy used fork lift batteries from the UK but find out why they are for sale and chack out the seller as much as you can.

Good Hunting.
Pete.

I've seen a couple of companies selling second hand batteries, re-con batteries etc but like you say, you never know if you're buying someone else's junk. The other thing is transport to Spain. I did find a company that would ship 24  2v cells to spain for £260 (shipping only).
I would prefer new and preferably in Spain if anyone knows a man who knows a man.

I have a bank of 12 x 2v batteries that I'm looking to sell
Some of them, if I'm honest have had it, but there are 6 cells that are in good condition. If anyone is interested let me know! I also have a huge generator 10kw for sale and a end generator which is almost new, up to 700w x 24 v. The wind generator comes with a great ling pole plus the wire tenors but needs dismantling. I hope someone is interested. Sarah 622487066