Well, new saddle held up very well, got the Spesh Alias 155mm. When removing the old saddle I did realise that there was wear on the right side only. Guess what!!! it was slightly off line with the nose pointing to the right of the top tube. So got one of my boys to line it up this time, better eyes etc. Did 106 miles on it and no chaffing problems at all. Bit harder on the sit bones at times, but not enough to cause discomfort. They'll toughen up and, as I lose weight, will receive less pressure anyway.
However, so intent was I on getting saddle on straight etc, that I totally neglected to match rails position. Aperitif picked up on fact that my knees were back of optimum for pedalling. I was also aware that I may have to raise new saddle slightly as was less padded and bulky than the old. Though wasn't sure as this would be offset by how much I sank in to each one. This all resulted in reaching Southend with a bit of lower back pain(slight) and quite a bit of pain in right knee.
Aperitif adjusted saddle with me, so raised about 5mm and, over 2 adjustments, moved forward on rails by 25-30mm. I suffered on return to London but some painkillers finally kicked in and I finished fairly well. Knee was sore last night but much better this morning. Went out for a 5 mile tester and no pain in knees, back or butt/nether regions.....very happy. Also made some further adjustments to handlebars via adjustable stem.
Thanks to all for the help, as usual, god knows how much I'd go through if it wasn't for the advice on here.