Thanks for replying - that's actually more the sort of answer I was hoping for - a simple technique to align multiple points and/or polys.
My weld attempt was futile in the end.I've discovered that there's really no substitute for correctly aligned geometry,and in the interests of developing useful modelling skills I started over (again!!)
This time everything appears to have gone very well and I'm thoroughly enjoying the feeling of satisfaction at seeing an error-free render.It'll be some time before I can readily apply the principles of correct geometry placement without closely analysing the invaluable examples contained in the marvellous video tutorials though....
