When we first started we chose the Outwell Hartford L (2 adults, 2 children now both just about teens)
I have to say that we nearly bought an eBay special (Rage) but thankfully reseached a bit more and didn't.
We had a good look about the internet - because believe it or not here in Cumbria there are not a lot of camping stores. We found a very good independant camping stre with an indoor display (Kendal Camping) and went to Yeomans (at Ambleside) and the staf there ver very very helpful.
Once we looked and felt the tents (and of course noted the prices) we changed our minds again, from Vango, and decided that Outwells seemed the best choice. Hunted the net for good prices and went to the local store and haggled. We have since bouth 3 tents from him and various kit so it was worth him doing us a good price for us
I then got hooked on canvas frame tents - could never afford new so bought second hand. Does it have to be a new tent? there can be some good deals around on a certain internet site.
You have to decide what sort of camping you are going to do - mainly weekends or weeks or a combination of both ?
How old are the children?
Do you want to sleep altogether or are you happy a different ends of the tent (vis-a-vis style)?
What is your budget for the tent?
Car space for transporting you all, all the gear and the tent? Roof box, trailer?
For a family of 6 you will be looking for an 8 berth really - though they say 8 if you are using air beds rather than mats then you will find it a squeeze in a 6 berth. Living area will need to be considered too because if the weather isn't too great then you may find yourselves spending a bit of time inside. Something that comes with it's own canopy bulit in or a small porch area is also a good idea.
If you have older children have you thought about a main family tent and maybe a smaller pup tent for one of the older children to sleep in. You can usually pitch a pup tent on your pitch for no extra charge.
HH is the figure to say how 'waterproof' the tent is. The higher it is then it should give more protection. 2000HH is OK for summer type camping but if going all year round then 3000+ would be better.
Better still would be the Polycotton tents (they don't have HH rating) and even better still Cotton (Canvas) tents (again no HH rating). For the latter 2 your £1000 would about cover the price of the tent.
SIG - sewn in groundsheet
ZIG - zipped in groundsheet
Footprint - not a complete necessity but very good for keeping the sig clean and far easy to clean when you decamp that haveing to clean the bottom of the tent. A tarp from a DIY type shop will do just as well but cut a couple of cm smaller that the tent footprint.
Carpet - again not essential, but it does make all the difference. Picnic rugs or similar will do just as well.
When you are first stating out there is no need to splash out on loads of gear. You will find you have lots of things at home you can take - we personally don't use sleeping bags but take duvets form home. We take pans from home and all sorts of bits and pieces.
Tent, something to sleep on and in, something to cook on, something to eat off/with, something to sit, lights and heating source on would be my basics - then there's the ehu if you go that route.
As you camp time after time you soon learn what works for you, what kit you would like to buy and what is usless and you dont need.
Tent - I would be looking at Outwells Norfolk Lake, Wolf Lake 7 . If you can find a Sun Valley 8 that would do you well but it was discontinued in 2008. Hartfords, Idaho (I think) are good too but being pod tents they are wide and some site will chare extra - but there are way more sites that won't so you just choose your site to suit your needs.
A new range is the Kampa tents. I have no experience of them but from what I have seen and read then they seem to be very good. HH is 4000, well spec'd and they are very appealing to the eye.
Have a look at the Studland and Polzeath both 8 berth and very similar to the Sun Valley 8 and Norfolk Lake in design.
Then again - what if you don't like it???? Hireing a tent and trying it out first could be a way to go or buying a cheap Halfords/Argos family package and going in the middle of summer for the first camp could be the way to go and then once you decide it's for you and the family then you can splash out on something good. If you don't like it then it's only a couple of hundred wasted (well you can sell on and get a littel of your money back) rather than nearly £1000 wasted.
If you are not that bothered about buying new then there are lots of good things second hand but make sure you ask lots of questions and see lots of picutres and the owner knows what tehy are selling/have taken great care of it before you commit yourself. I have never bought a dud off the auction site (yet).
Hope some of this has helped - it's just from my experiences and not hard and fast rules
Good luck with your decision and please let us know how you get on/what you decide and don't be afraid to ask and ask and ask before you commit and then look around and haggle. Find a good independant dealer if you can as they will give good unbiased advice and you will return to them time and time again and they are more likely to move a little on price or throw in things as extras for the price they are asking because they would like you to return everytime you buy new kit.