Sorry how is it a higher risk if the net result is that the monthly payment is lower than the existing one?
I'm at greater risk of not paying Â£340 a month than I am of not paying Â£485?
You have a history of poor financial decisions according to your previous posts. There is no guarantee with debt consolidation loans that a borrower will use the 'new' loan to pay off the 'old' one, so you could end up with twice as much debt.
Also, you are forgetting that the sole purpose of banks / building societies are to make money for their stakeholders. They're only interested in profits. If you're paying Â£485 a month to them, what's in it for them to allow you to re-settle at Â£340? They're going to be losing out on Â£145 a month. Not sound business sense.