try a good spray grease on the slides / tubes
Thanks - all I has was WD40 in the shed, I've used this but will invest in some silicon grease or similar vehicle orientated product. It may purely be a lack of use that has led to this.
Is there anyway to get the lube to the inside of the tubes easily?
The glass is back on and it is still opening/closing. I'll make a point of continuing to use to try and ease some more.
Thanks again for all replies. Enjoy the hot weather if you are lucky to have some.