Just keep in mind that because they say it's enabled doesn't mean that it's usable or in fact supported.
For me (on BT). I get assigned an IPv6 address and so do my devices but all IPv6 traffic is getting as far as the first BT network address and then is dropped. If you want to see futility in action you can see my thread over on the BT forums.
EEEKKK. Im not BT support, but your router-config:
WAN IPv6 Address 2a00:23c5:7603:eb00::1
WAN IPv6 Gateway fe80::ea4:2ff:fe3e:1
LAN IPv6 Address 2a00:23c5:7603:eb00::1/56Is wrong. Though shalt not have the same address on WAN and LAN. Maybe your CPE supports DHCP-PD 'not really'. Anyway, for LAN a /64 out of the delegated /56 should do. Try something with a working IPv6-Stack as CPE. Anyway ... one 'standard way' (like I implement it for my customers) is to hand out WAN-address via SLAAC (or DHCP/Single adress) and provide the DHCP-PD only for use on the CPEs lan Side(s). Its slightly OT, but as featuring-v6 is one of my pet-projects try:
1) if you can receive an /64 address via SLAAC (yes, you don't have a working v6 on the lan-side then). Your CPE shoud then have a v6-address on WAN, as well as a v6 default GW (and the CPE[not your computer] should be able to ping the later) if that works
2) configure the LAN-side for using the a (sub)network attained via DHCP-PD (over the WAN). The prefix for DHCP-PD should be different from the Prefix in use on your WAN-interface
For those wanting a test-for-IPv6 connectivity: <http://www.ipv6-test.com/>
Its pretty basic, has nice Red/Yellow/Green colourings and is understandable. But it's not fit for any debugging, it merely gives you hint where Problems arise from (given you already have a working v6 connectivity, that is).