I've just entered into the Octopus GO tariff, it's called 'Octopus Go June 2018' so I expect you are still on this valid tariff, so it's just your 12 months 'fixed' that comes to an end.
You should just be able to renew a 12 months fixed at the same rate, (although the gas price may well be different).
If you joined a year ago, it probably took a while to move over to GO, hence your 12 months started again for the electric side, so they are out of sync.
Regarding bills creeping up...
During the lock down I've been working from home (with the kids running riot), and I've noticed quite a jump in bills, but it's directly related to our energy use. We must be 10 to 20% higher usage on electric, and marginally higher on gas.
I use more, it costs more! (But I've saved a fortune on petrol, while I wait for my I-Pace...)
I-Pace EV400 SE, fuji white, ebony interior, heated front seats and privacy glass.
I think it's built, it's apparently on it's way, will it arrive this year...?