I used to sell lifejackets and can confirm it's a very good price indeed, especially for spare canisters. However,to be fair to Fox they supply Crewsaver lifejackets, which are used by the RNLI and are generally reckoned to be the best of all.
I've been to the Crewsaver factory and seen demonstrations of all their product line. I even jumped into the pool fully clothed wearing a lifejacket - and I don't swim!
One point that Crewsaver stressed was that when wearing heavy winter clothing we should go for 275 Newtons of buoyancy. 150 Newtons may not be sufficient to turn you the right way up if air is trapped in the wrong place, so you could be floating face down. It can be difficult enough to turn over anyway, but unconscious it's impossible!
Don't say it won't happen to you. A friend ducked to avoid a seagull, slipped and banged his head on the gunwhale. He ended up in the water and out stone cold. Luckily he was wearing an automatic self-inflating lifejacket, which saved his like.
I like the idea of the green colour of the ADEC - ideal for fishing flooded rivers when undercut banks can give way. Crewsaver make a 150 Newton in green for Barbour but it's much more expensive.
I've also used a self-inflating fly waistcoat from England's but the zips kept breaking. They even wanting me to pay for the repair even though it was for review! Strangely none of the magazines I wrote for at the time wanted to carry the review!