I extended mine last month due to not having my new wheelchair in time to check the boot sizes of prospective replacements. It just said I am extended for 2 years, but can change at any time within that period with no penalty.
Can I just ask, did you make the 2 year extension online or by phone? Also, did the wording online (or said by the operator if you called) specifically state that you could change at any time within that 2 years? I know that’s always been the case previously (you could extend by 1 or 2 years and change at any time within that) and hopefully it still is, as I may wish to do this myself, but as mentioned earlier I was specifically told yesterday that the automatic extension facility is reducing to 6 months and anything longer is only by exception. Knowing my luck, the change will have been implemented by the time our order window opens in April ?