Finally sussed where my endurance has gone.
I haven't cleaned and polished my bike for ages which must be what is slowing me down!
Gave a good clean and lube tonight (my bike that is) so I should be rocking tomorrow.
I have removed the Rido Original saddle that I got for a song on
ebay and have put my Specialized back on.
The Original is really a bit 'sit up and beg' but I have got my hands on a Rido LT and I'll be giving that a shot when it arrives.
I may have a bit of an internal trauma somewhere as even sitting can get a bit uncomfortable sometimes nowadays but I have an appointment with a specialist (not Specialized) next month so hopefully I will be able to 'get to the bottom' of my problems.
I've been moving my saddle so much recently I have had to reset it tonight to the 'standard position' using the good old tries and tested straight leg and heel on pedal for height (to make sure you don't rock) and the back of the knee cap just behind the pedal axle with the pedals level for fore and aft.