Take Dave's advice Tony. LiFePO4 is bulky, heavy and needs installing inside the frame securely and preferably with padded shock protection.
The 48v 11.Ah bottle batteries are easy to fit, robust, and if you wait untill you can buy the one from Eclipse, perfectly fine with the BBS02 750w 25A.
I know you're getting itchy feet, but buying the wrong battery will taint your experience of electric biking and cost you in the long run.
Think of warranty. Eclipse will be easier to deal with than BMSbattery, if something goes wrong.
Handbaked recently had a problem with his bottle battery, which he bought from Eclipse. I believe they are sorting it out as I write this.
If the same problem occured with BMSbattery, I'd hate to think how long, if at all, the problem would take to sort out.
Dave buys his from BMSbattery, but he's a tinkerer, and can sort out electrical and mechanical problems quite easily. If you are not confident with soldering and electrical problem solving, then buy from the UK.
I'm not saying BMSbattery will definitely sell you a dud, but the potential is there.