I was offered Fibre at up to 45MB with a minimum guaranteed speed of 35.
I jumped at this because I was stuck on 4.5 with ADSL.
Line was duly upgraded and maximum sync speed was 2MB. Thankfully was able to get back to ADSL without charge.
It turns out that their records assume you are a maximum distance of 500 metres from the nearest cabinet, I live in a rural area and am about 3500 metres from the cabinet.
FTTC falls off much faster with distance than ADSL2. So although I was further from the exchange than the cabinet I got a worse service.