Your contract is with Evesham, and as you state, its for them to sort the problem out. But having said that, it is usually the case with monitors, that the manufacturer is the better route to take. The manufacturer may supply a 'swap-out', in which case they will send you another monitor. One thing to consider with a swap-out on a nearly twelve month unit, is the replacement will most likely be a refurbished, but fully guaranteed unit, not brand new.
Make sure that you have confirmation that Evesham have instructed you to contact the manufacturer. Failure to do this may limit your claims later on.
On a point of interest, how long is the monitor's warranty- One or Three years?.