Many thanks Oliver ... I take that I need to spread the 'latches' on either side of the elbow fitting which will then allow the elbow to slide out for replacement of the o-ring ..... that's a bit of luck

cheers and thanks again

ps. I did have a chance to compare a new radiator hose with my old one (was going to replace all the hoses) and did notice it a lot 'stiffer' but simply thought that my old one was simply old and worn. However, was to cheap to replace it .... maybe I lucked out wrt radiator by leaving it alone