Looked everywhere to find a charger for my Star n9770 batteries without success, until I found this one, it will take literally any size phone battery, provided the battery terminals are all on one end of the battery, I've uploaded 3 pics so you can see it working. It has an display at the bottom to show that its charging. You'll need an adapter for your 13 amp socket or there is also a usb connector on the side of the unit.
I bought this through the Amazon seller BigBargainStore, who I thought at first glance were in Northern Island, but on digging a bit deeper, I find that all their items are shipped from, you guessed it, China. It cost me the princely sum of £2.79 and it took 15 days to arrive, obviously its not going to last for ever, but looks quite sturdy for the price, I did have to adjust the terminals a bit as they did not align at first with the connections, but seems to be working fine. Have not tried the usb connection as I cant find a suitable cable at the moment, will update this when I find it.Big Bargain D11 USB LCD Multicolor Universal Seat Charger For Phone Battery
Edit... It does work ok, but is quite slow, takes a few hours to charge fully. Also works with usb cable, you need a male to male standard size usb for this, couple of quid on amazon.