Hi MoleandRatty
Top priority get a pollytunnel up as soon as possible, It replicates the weather down south where most of the kitchen gardeners live and most of the advice applys to.
I live over by Peterhead and only a couple of hundred feet up but it gets awfully cold here for longer than most other gardeners.
Generally I grow the same as every one else but you need to be aware of late frosts so don't be in too much of a hurry to get anything in the ground.
You won't be able to grow Sweetcorn, squashes, outdoor tomatoes or any of the cucumber family, that's why you need a tunnel
Root crops are very successful for me, carrot fly is a problem but I now grow them in cattle lick pots ( about 18 ins in dia and a foot high) plenty around as I'm in the middle of cattle country.Parsnips are always a huge success I've just dug up the last of them to get the ground clear for the spring which doesn't arrive here till the middle of April at the earliest and is when I put my first spuds in
I get good crops of Cabbage, Sprouts but not much success with Broccoli but may be that's just me.
Peas do well but we are not bean people so can't tell you about them.
Onions grow well but there is always the problem off drying them off not enough heat towards the end of the season and the tunnel is too damp at that time of year to do the job properly although that's where I always put them as there is usually a lot of them and not enough room to go anywhere else
I grow my own sets by planting up a tray of seeds and bringing them on in the tray, watering and feeding until they are the size I want then stop that and let them dry out ready for next year Bedford champion is my choice though I do usually buy a net of something else as well. I also grow onion seed on in modules, I like to keep all options open. Leeks are just as easy and all the usual varieties I have tried do well.I have Garlic inside and out of the tunnel but you probably know that one of the most succesfull garlic growers in the UK is just 20 mile from you
I have Asparagus in the garden but the best place is in the tunnel, mine is 14ftx 30ft and I have two short rows of 4 plants in a row, home grown Connovers colossus.The rows are only a 18 ins apart but the amount of Asparagus I get is fantastic,
Soft fruit is a must up here, all grow very well, If you have a sheltered spot Victoria plums do very well and when you have a tunnel the worlds your lobster

In the tunnel I have Nectarine, Blueberries and an Apricot.and of course a couple of early pots for a spring treat along with 6 Strawberry plants.
I have a propagator in the tunnel made from an office desk with the top built up with the kind of 2 wall plastic they use for conservatory roofs.and the heating in it is a bedroom tubular heater of 80 watts. As you can see I have mains electric in there and also water which is fed from my garage water butt 30yds away, the electric is from the garage as well. Made an extension lead using armoured cable and ran it with the hose pipe 6 inches under ground. Now waiting for dire warnings from the Elf police about safety but I just tell them that it's OK as I wear my rubber nickers when i'm spraying water around.
My don't I ramble on, anyway don't forget the tunnel get a good sized one up as quick as possible and remember whatever you put up next year it will be too small.
Arthur e