Terrific - SWW can't be sure where the main goes, although they don't think it's directly below where the first post has to go! I think I feel a dwarf wall with the posts built into it coming on, or raised concrete bases made with formers.
Many thanks for all your help and comments folks...
Thanks Deluks - putting the post somewhere else isn't an option, sadly it will make the whole thing look like it's been plonked in at random. The sewage pipe crosses the fencing line about halfway along which can be accommodated, it's the mains water pipe that's the biggest problem. Like your...
I have just had a (very dead) hedge removed from my front garden and planned to replace it with a fence. Exploratory digging has revealed sewer drainage and a mains water pipe running about 8 inches underground exactly where the fence posts need to go (typical...) so it is not possible to sink...