I had a thought about the annual 'Gold' travelcard (oyster), I bought mine in November last year and paid £808 for Zones 1+2, this went up on September 1st to £856. Now could I have bought my travelcard last Nov, use it for 10 months, cancel on August 30th & get a refund for unsed days/months. Then get another yearly one the next day which would be at the cheaper price i.e. before the price rise on Sept 1st? You could save yourself £48 doing it that way, I can't find any info on TFL about this.

Edit: Yes I now have found it, and this doesn't seem to be a winner as TFL add a special charge for doing the refund and then also don't give you back the number of months divided by twelve. They do it by a formula and you might get nothing in a refund if you are near the date your card runs out.