I spent a couple of hours this evening balancing the rads,although there was a bit of guesswork involved as i believe you are supposed to start with the one nearest the boiler and work down to the end of the line. It worked . I identified the in and out valve of each rad by turniing both off until rad cools down .then turn both on and see which one gets hot, that's the in valve,I marked the"in " with tape and then turned the "out"valve off. I repeated the process with every rad in the house. At this point every rad has the "in " valve fully on and the" out" valve fully off . Then I went through the rads one at a time in sequence(ish) and turned the "out" valves on just enough for them to get hot(sometimes only a quarter of a turn)this seems to regulate the flow of hot water to each rad ,thus leaving more pressure in the hot water pipe for the rads near the end of the line.it's still not perfect but it's much better than it was. A bit more tweaking and hopefully it will be better still .also aplumber told me that this is a common enough problem and it's usually an inadequate pump that's to blame.I suppose I could of hired a plumber to sort it out but moneys tight these days, thanks for all the help good luck!