You can buy a house wherever you like. Don't forget that it is a condition of your contract of employment with most airlines that you maintain a contact address within 90 minutes normal travelling time of your assigned base. This means that you can report for duty (scheduled or called out from standby) within a maximum of that time plus around 30 minutes.
The reality is that even for people living on the edge of this requirement road conditions these days often mean the actual driving times can be very much longer particularly during the rush hours.
If you are working long haul where travelling to and from work is a small part of the overall duty cycle it may be feasable to reside a long way from your base. On the other hand short haul or charter flying may involve considerable elements of commuting within the normal duty cycle. Often this will involve long duty days with minimum rest between flights. This will do nothing to add to your "quality of life" if you then get to drive for 4 hours a flight cycle with insufficient sleep in between. You would need to maintain local accomodation near the base.
The cost of housing in the south east ( as well as some other areas ) is certainly a major problem and very much so for people like Nurses, Police officers and Teachers whose average income is often much less than ours. Property prices like most other things are market driven. Demand in the East midlands is lower and the supply is better. unfortunetaly this is not the area with the greatest employment opportunities.
The cost of commuting in real terms would add a lot to most peoples outgoings if they had to drive over 300 miles a day to and from work. It would certainly add a considerable amount of cumulative fatigue to their lives. This is why most people don't do it, coupled with the fact they may be contractually prevented from doing it.
Obviously only you can decide if it will work for you. A bigger house may seem attractive in isolation, but if it is the only reward for a poor quality of daily life it may be a major price to pay.