I calculated about 40 month win per month so about £240 gain on SVR over summer. (electric only, more with gas on top).
If I took the deal its benefit would from Oct onwards, taking it and exiting before then would just give me the worst side of it? As SVR seems a clear winner from April-Oct, like you said its predicting what will happen in Oct.
Also bear in mind I use very little gas. I think most of the hike in Oct will be on gas. Notice how in the figures I quoted the gas unit race skyrocketed.
Also. Yours is only a year. So the benefit is likely to be minimal.
Mine was 3 years. Which has a lot more leg y room.
It's probably 50/50. If it was 3 years. I'd say go for it. 1 year.. Much more unimportant