can anybody tell me the difference between a micro bore radiator and a standard central heating radiator as i cannot get the same type of microbore radiator with the feed and return going into the same side .
A microbore radiator has smaller passages. The manufacturer made it convenient to place both inlet and outlet close together. Another type of radiator can replace the microbore by repiping. There is not a great difference in the heat output when comparing similar effective exchange surfaces.
To use a valve with both flow and return microbore pipes connected to it, the radiator has to be a type where the insertion tube can be placed within the bottom horizontal channel. The reason for fitting the insertion tube is to provide separation between water flowing into the radiator and that flowing out of it. If this tube is not fitted, water would not enter the radiator/very poor flow into the radiator, since the valve inlet and outlet are concentric within the union that screws into the radiator.
On some radiators, the valve connection is in form of a “balled” connection welded onto the rear of the panel. This type of radiator does not allow insertion tube to be fitted, therefore it is only suited for single connections be they microbore or small bore. Insertion tube can be an 8 mm plastic or copper tube. (for you the size may differ).
I hope above will help Thankfully we REAL plumbers do know heating LOL