Hello,, Problem finally solved!!!!!!
Nothing to do with pump!!
Nothing to do with non return valve!!
Decided to take it apart to have another look and I saw, for the first time , water leaking back from a fitting just before the water tank lid! So it was a broken plastic fitting that goes they the lid and it was opening up more and more every time pump moved or I pushed and pulled!! Unscrewed it, put length of hose with jubilee clip on and immediately sorted!! So I have now the best water pressure coming out of taps I have ever had, !!!! I was lucky the fitting was broken the water tank side of the lid so all water stayed in tank!! Bonus !!!!!!
Just been reccommended a good mechanic to the south of Seville so I'm going there tomorrow, so helga can have a treat as well !! Xxx.
Gonna treat her to an auto gearbox oil change, oil and filters under the bonnet too!!!! And I want to give her a system and injector cleaner, additive!! She should like that!!