Do Zen easily allow you to switch to their lower price plans

I signed up to Cityfibre 3 months ago and have since then seen the prices on their current plans drop by £5-8. Do Zen change the prices on the ongoing contracts, or can I ask for it to be changed without too much quibble? I'm happy for it to be reset to 24 months of contract length.

I still have 3 months free from their September signup promotion plus £150+ of compensation credit to use up due to delays on Cityfibre's part, so I'm unable to see what the price is on my bill yet. But if it's old pricing then I will ask to be moved after 6-7months if it can be easily done.