Fibre To The Cabinet (FTTC) operates using VDSL from a street cabinet rather than ADSL all the way from the exchange. VDSL uses different frequencies and powers to ADSL but is otherwise very similar technology. VDSL can provide speeds over 100Mbit/s on very short lines. The speed available drops off quickly with distance – but this is not usually an issue as cabinets are usually close to premises. There are cases where FTTC can be slower than ADSL all of the way from the exchange.
It is important to realise that the above is a technical statement about the VDSL technology. An actual service will achieve a sync speed (which includes various overheads) depending on the line length and quality and other factors, and may even change over time. Services are available with speed caps set at 40Mbit/s or 80Mbit/s download, so higher speeds are not available even if the line can support it. To assess the likely speed of your service, please use the availability checker.