looking to reseal windows to stop drafts

If you mean where the frame merts the wall then it's a easy job it's just cut out the old silicone with a Stanley knife and reseal with a good quality frame sealant, if it's the unit has water in between the pains they need replacing, if you mean the rubber seals the easiest thing to do is cut a small piece out and take it to a good builders (Travis perkins, jewsons, etc) to get a exact match and pull out the old and push in the (if it's had to push in use a little washing up liquid and water in a spray bottle will help Hope this answers your question Kieran

My answer will be exactly the same as Keiran