Failed to sort out the washer jets. One had plenty of oomph, the other was pretty lacklustre. Found that the lacklustre one was missing the one way valve (how does a part like that just go missing??!!), put the valve in line, no joy, changed the washer unit, the drivers side starts suffering low pressure passenger is working fine, swapped the outputs around on the t piece, passenger side not working, drivers side has huge pressure so both washer units work fine (no blockages) it's just the pipework which has no leaks and creating poor pressure on one side. T Piece is fine too so I'm stumped! Also took sunroof off, checked all the downpipes for flow and changed the sunroof seal.