They have  called for the Speed advertised to be the actual  speed customers can expect, not the maximum speed they might achieve.

The average UK Broadband speed for example is 6.2Mbits/s against the average advertised speed of 13.8 Mbits/s 

Average download speeds remain less than half of ‘up to’ speeds advertised by some ISPs, particularly for current generation copper-based ADSL services. 

Ofcom is recommending that if speeds are used in broadband advertising, they should be based on a Typical Speeds Range (TSR), so consumers have a clearer idea of what speeds to expect. 

Ofcom also recommends that the TSR must have at least equal prominence to any maximum ‘up to’ speed, and that a maximum speed must be used only if it is actually achievable in practice by a material number of consumers. Ofcom is also setting out what the TSR might be for each technology used to provide fixed-line broadband.

It is worth asking questions when taking on a new ISP promoting "speed of light" technology to see where they stand with their typical speed, which may not figure in their advertising