Your max data rate is shown on the home hub/
Maximum data rate:11.829 Mbps / 52.004 Mbps
So, once DLM is reset, you should get a connection speed close to what you had before,
Talked to BT helpdesk and they say DLM reset is noit required but that an engineers visit is needed as they think they had fixed the issue outside my house but they agree the speed is very low. So I will await that to happen and see how it goes from there.
Thanks to everyone for the advice.