What have they done to my CH?

Hello,
Potterton Puma80 combi - small flat, only 4 rads, working perfectly both CH & HW until a couple of days ago when builders came in. Part of their work was to reposition one of the rads from one wall to the opposite one. They did that and since then the CH hasnt' worked properly - the nearest rad to the boiler heats up, the next 2 are lukewarm, the last one (the repositioned one) stone cold! And the boiler's making "clunking" noises.... the rads have all been bled a number of times (but not the pump). Is there anything I can do myself to rectify this mess and get a bit of heat (until Monday when they will be back and I'll give them hell???)
Thanks
marina