@RedMango,
Yes it means rads larger than current heat loss calcs would prescribe.
Radiator sizing apps, catalogues and charts currently use a 50° deltaT (difference in temperature) between the desired room temperature and the mean (average) water temperature in the radiator.
This is based on gas boiler having a flow temp of 80° and a return temp of 60° (20°deltaT).
1. water entering rad = 80°
2. Leaving rad = 60°
3. Mean water temp in rad = 70°
4. Desired room temp = 20°
5. DeltaT between 3 & 4 above = 50°
To make better use of condensing boilers and reduce energy wastage / burning of gas, green issues, through partL building regs, aims to lower the flow temps of boilers to 55° with a return temp of 35°.
Using the method above (1-5) gives a result thus...
5. DeltaT = 25°
Which is half of what radiators are currently designed and sold at.
In simple terms you do a heat loss calc for a room, choose a rad that has the appropriate KW output for that room (which will be based on a deltaT of 50°) then you double the KW output and make a new selection from the catalogue based on that, to see what dimensions/type of rad will deliver that output, thus heating the space to the desired temp using the lower flow temp of 55°.
As for whether you need to comply or not, it would be in your best interest to do so now, during this opportunity of a new install, because in @10 years time (sooner if law changes) you will need a new heat source in your forever home and by then, it's pretty certain you will not be able to achieve flow temps of more than 55°, thus rendering your heating system insufficient.