Thank you all for your replies. Yes my cue commands are "do wees" and "do toilets", which has happened from the beginning. I've just spend 2 and a half hours outside after talking with a friend of mine who has five dogs currently but has had many more, some as puppies and others as very disturbed rescues. She made a suggestion thus, give him a food he will wolf down, such as the Nature Diet I gave him when he was teething. Then when he's finished feed some more and a few treats too. Then just take him outside and walk him round, play and play the waiting game. Well he managed one wee after a hour then nothing. I came upstairs for a wee and so did he, d'oh! However, the poop is still brewing. He's currently spark out but give it until he awakes then straight downstairs with him. Once he's finally performed she agreed with the suggestion of leaving one in the longer grass to get him in the mood. She obviously does not agree with slight over feeding long term but just for a few days to have a little more control over being able to second guess him. As long as we dodge the showers we are ok! BTW he's only 21 and a half weeks old, so I know he's still young but he'll be happier if he gets the hang of this quicker. He's doing amazingly well in other ways.
Nicola: I'll give that a try. Sometimes he goes an hour or two without a wee and at others two or three an hour.