This year is my third outdoor grow in england. Last two years have been decent, and I can give you some help if you require.
I always grow in a greenhouse, I haven't tried it without it, ,mainly because i'm too afraid it'll piss it down and drown my plants. So yeah, get a greenhouse! I got mine from wilkos, 6x4ft = £225. Does the job for me. Wilkos also sells these set up greenhouses, haven't tried one myself, but they're basically like tents will transparent plastic.
I'd also recommend starting inside too, as mzn is doing, (and as i am,) and moving them outside generally a month later; or whenever the weather is hot.
Lots of nitrogen too, helps keep them strong and tolerate shitty weather.