cjpd wrote:
I live an old house with sash windows. Is there a cheap and easy way
of stopping wind coming through the space where the top part slides
over the the bottom one? It would also help if the solution was such
that it stops the two parts banging into each other when it is windy
outside.
I was wondering whether insulating strips could be attached - but am
worried that they will be very difficult to fit and will stop the
windows sliding properly.

Mighton Products, as mentioned elsewhere. The parting bead
replacement is very useful, although the "groove" it goes
in is usu. a bit wide for the replacement bead, and needs
packing. Use "E" rubber strip on the top of the "outside"
sash. Don't draught-proof the meeting rails, or the bottom
rail. Cut some softwood wedges, or use cardboard, for a
temporary fix for "rattling". You can do a bodge if you
want a winter-only fix for some windows by using 21-day
masking tape to cover the gaps! A1 sash fastners (Brighton
Pattern) are OK for the meeting rails, and secure, too.
Brass is best, £4.5 approx. per fastner.