UPDATE: Before anyone waste's their time on this, as you'll see in the comments this offer seems to be account specific and not available for all business users. Also note that Amazon Business have two listings, so if you really want to check then search "Makita BL1840B" on the Business site. Otherwise, sorry to disappoint!
Was checking for a 5ah Makita battery for my mower but spotted this which seemed too good to pass up. Seems to be similar priced to the 3ah deals that are usually posted on here. It's on Amazon Business so you'll need to be registered as a business seller. Comes up at £19.99 (ex. VAT), which is £23.99 (inc. VAT).
I was a bit suspicious because it's very cheap and Amazon have another listing for the same battery for around £50 too. I contacted Amazon and they weren't able to explain why there's two listings, but said that it's sold by Amazon and I can get a refund if any issues so I've taken a punt with it.
Doesn't beat the 5ah's posted a while back for a similar price but think it's a good deal regardless.
Forgot to add, it's free standard delivery