Ferry to Guernsey: how to get a cheap fare? - NowWheels
I am planing a car trip to the channel islands next month, to see some friends and soak up the sun, and am looking for advice on ferries.

So far as I can see, Condor Ferries have a monopoly on ferries from the UK to the Channel Islands, and their website offers me a return fare of £210. To be honest, that seems not too bad, because it's a lot less than I would have to pay for a shorter crossing on the Irish Sea (Holyhead to Dublin).

However, I seem to recall reading something on this site about ways of getting ferry bookings more cheaply, some website that offered discounts, or something. Does anyone know if there still anything like that, and whether it applies to the Channel Islands?
Ferry to Guernsey: how to get a cheap fare? - oldnotbold
CF will have no need to sell through/via a discounter if they have a monopoly.
Ferry to Guernsey: how to get a cheap fare? - tr7v8
Their doesn't seem to be any cheap crossings to Guernsey, cheaper to fly & hire a car.
Might be worth try the Ferry Travel Club for a cheap fare but I couldn't find one a few years ago when we went.
Ferry to Guernsey: how to get a cheap fare? - hjd
You can get a small amount of cashback by booking through www.quidco.com - remember to clear cookies first though.