Thanks for all the advice everyone. It made me doubt putting them out last weekend, so I didn't. They're still in the house being pampered! Good thing is that their growth has slowed down now, so space situation won't get any worse than it already is. They are using the whole room to roam anyway, fence not much of a barrier anymore, they're good flyers! Well, some of them, the sussex and blue ranger are more squat and clumsy.
They are sounding like proper hens now, clucking away! And good thing about keeping them in with me is they're becoming more tame everyday
I know they won't be going out next wknd either, more rain and wind coming, so they'll be with me till the half term where I'll be able to put them out gradually during the week as you suggested. I'm sure by 14 weeks they'll be ok, as the breeders chicks have been out since 3 weeks ago. Also some of my pupils I teach biology to are farmers and a few of them have growers who they've put out couple of weeks ago and they're younger than mine!
We have been lucky here in North Wales with the weather, whilst it has been raining and fairly windy, it hasn't been that much worse than usual, just much warmer than it normally is this time of year.
We have started to build a shelter around the outside coop, made out of pallets, and I'll ad some plastic sheets for extra wind buffering. I'm hoping that will make life more comfortable for them.
As for the car port I had in mind, the stupid coal man went and dumped our coal there because he ran out of bags.. So that option is out for now.
Also want to mention that just around the corner from us there is a small holding with dozens of chickens that have coops in the middle of a few acres of open fields, and the only shelter they have is a few trees, and they don't have any problems, so the extra precautions we are taking I feel is just that, extra preacautions. But at least it will give me piece of mind.
Oh as to mowing the grass.. Lol, would take a while to mow the field! But I will make sure when they're out for the first time they have been fed before hand. They are loving the chick grit now anyway and I have been introducing greens in very small amounts. They are not much interested in eating yet, only playing! They regularly have games where one of them finds a 'treasure' (normally a moulted feather) and run around with it whilst the others try to grab it! Very funny to watch. There is no clear leader in the group yet, they all hold their own when challanged with the neck extended feather ruffling of one trying its luck. That's as far as it goes though, they never hurt each other for which I'm glad!
Looking forward to getting some eggs now, in 9-10 weeks? I presume they'll start laying after 20 wks?