We stock some North Sea at Jump the Gun and of their small range it is all made in the UK. Lots of people are making a submariner of varying quality. I don't think North Sea are an actual manufacturer but they are having it made here.
If Outdoor knitwear are making their jumpers in the UK then they don't seem to be very keen on telling us. Yes it looks like the wool is British but knowhere can I find on their website says "Made in UK". British designed often leeds you to think they are manufactured overseas.
If you buy one like i did you will find that the label states made in england, they are part of a bigger company TW KEMPTON who if you check out their website you will see they have been supplying the British armed forces for about 50 years,mainly with sweaters.