Amazon Basics AAA High-Capacity 850mAh NiMH Rechargeable Batteries (Triple A), Pre-charged, 8-Pack - £5.61 (£4.77 Sub &Save) @ Amazon

Yes. Allowing for some inefficiencies with the charger these take about 1.5Wh to recharge, or about 0.05p per recharge.

To put into context how little energy these have if you wanted to run your tumble dryer for an hour using these you'd need 3000 batteries... 50 every minute.

These are pre-charged. So will have a bigger separator that reduces self discharge. Pre-charged rechargeable batteries are often preferred for this reason. You can charge them, store them and they’ll still have a decent amount of charge when you reach for them.

Did you mean Amazon Warehouse (customer returned goods sold again at a lower price) or just Amazon's own branded stuff? I've had good experience with Amazon's own branded stuff, it's all been decent quality, but have had some bad experiences with Amazon Warehouse purchases.

It's called monthly subscribe and save as you will have your products delivered every month, but you can choose which product you want each month, you can have delivery every 2 weeks up to every 6 months. The key to the success is to have 5 products on monthly delivery to enjoy 15% discount.

You can also cancel product/s you no longer need without any problem. (edited)

Same works out a little better

Even the chinese stuff is good enough. No bad options here. Japanese batteries are better but not as much better as you think.

Don't see why not but correct me someone if I'm wrong. They sell low capacity rechargeables designed for garden solar lights so that's the same principle.