Hi,
I agree with Lesley. I book my Newcastle to Heathrow flights myself as soon as possible, this works out cheaper than booking later on, and also ensures you get a seat on the plane. Just make sure you opt for checked luggage as British Airways now do a cheaper option whereby you can only take hand luggage (no suitcase checked-in). I'd also recommend staying in a hotel before and after your holiday if the flight times of your main tour leave early/arrive back late, especially if they're not with British Airways as you will need to change terminals at Heathrow. I use the Travelodge and get the Hoppa bus to and from the airport, but the Premier Inn is good too.
If you need any more information please let me know ?.
Regards
Caroline