Thanks mummymeister. Sorry for the delay in replying. I hadn't seen the bigholidayhome website before , prices are all over the place but there's a distinct lack of choice for us in the north east and in our price range. Will keep looking.
Have a look at 2 websites that we have used in the past - groupaccommodation.com and bigholidayhouse.com. Both have a good selection of properties and we have found both big houses where we can all stay together and also groups of cottages so we can have a bit of time apart. good luck i am sure you will find something. also national trust might be worth a look to but they would mean pushing the budget boat out!
We go every year for a week in October (half term) to a big house with between 18 and 20 people. We've done Lakes, Dales, Somerset, Herefordshire, Staffs etc. We are looking for something in NE England or southern Scotland next October. Haven't found anything so far but you never know. If you know of anywhere then please let us know. Ta in anticipation x