Moving Radiator Pipe

[GeordieSteve]

Hi
The last and lowest radiator on my heating system has the pipes tight to the floor and i need to lift them to put new flooring in. There is no play in the pipes so will have to cut them and rejoin them. I have a Bosch Wocester heatslave oil fired boiler and was wondering:
a) will i have to drain and refill the whole system
b) if yes to a, then how do i go about this

any help would be greatfully received

thanks