right,took it to tim frys today,flow check went fine,pointed out viscous fan wasnt working as well as it should be,seeing as everything else has been replaced i went down that route and forked out for a new one.
came home,changed the oil and filter,fitted the new fan and you can hear the difference immediately,temp gauge now sits just under half and up the offending hill where its been heating up before it only goes up to half and sits there for a few mins before returning to its previous spot...
granted its not quite so hot today as it has been,outside temp showing 18 as opposed to 20/24 like it has been...but fingers crossed thats sorted it,will find out sunday when the trailer goes back on.
thanks for all the hints and tips so far tho guys,much appreciated