Picture London's housing market as an octopus (bear with me). At the heart is prime central London, where prices defy the downturn. Radiating outwards are tentacles of prosperity running along the main arterial routes out of the capital. These are the traditional migration paths of equity-rich Londoners fleeing the city in search of a more green and pleasant way of life and they are relatively recession-proof, too.
But proximity to a motorway does not always equal strong prices. "You need to have really good housing stock, good schools and great access: that is what delivers a premium," explains Lucian Cook, director of research at Savills estate agents. "These are the first places where you really get out of suburbia and into towns and villages with a distinct personality. I expect these areas to perform strongly over the next five years."
High-value areas along the M40
The towns and villages off the M40, which slices through the Chiltern Hills, are a prime example of a stream of wealth trickling out from central London. The most extreme case is Gerrards Cross (average more than £850,000), but there are also more affordable options such as Wallingford in Oxfordshire - a thriving market town within an hour of London and with average prices of £315,000.
Cook has analysed the region and sees a north-south divide emerging as the M40 winds out of London. "There is a premium for homes to the north of the motorway where you are tight to the M25 - places like Beaconsfield, the Chalfonts, Gerrards Cross - but as you go further out it becomes less clear," he says.
"There are then some very high-value areas to the south of the M40 around Henley-on-Thames, which is not replicated in the north, apart from in some stand-out places like Princes Risborough."
Louise Batten, manager of Allen and Harris, says you could find a Victorian cottage in the Thames-side town of Wallingford from about £280,000, a Thirties detached family house for £450,000 or - for the country dream - a five-bedroom barn conversion for around £1 million. This is a classic market town, and a lot less tourist-happy than Henley-on-Thames, 10 miles away. Its downsides are a lack of station (although Cholsey station is five minutes by car and Didcot Parkway about 15, so you can make it to London within an hour).
Another major issue is that its senior school, Wallingford School, could only manage a "satisfactory" Ofsted report, although the area is stuffed with private schools.
To get closer into town, Gerrards Cross and Beaconsfield are obvious choices, with direct trains to London taking half an hour - although you will pay for the privilege. Nick Ingle, of Savills Beaconsfield, points out that both benefit from beautiful surrounding countryside and great schools. "Both villages, and in particular Gerrards Cross, are very popular with international buyers, being only 12 miles from Heathrow. Coupled with the English countryside that adds to the appeal," he says.
For a more rural lifestyle, Ingle recommends Coleshill. "It has all of the trappings of the quintessential English village, together with the communication links of Amersham and Beaconsfield."
One cloud on the horizon north of the M40 is the Government's proposed High Speed Rail link which could slice dangerously close to desirable towns like Chalfont St Giles.
Safely away from the rail link is Thame, south of the motorway, which is attracting interest thanks to an imminent upgrade of its rail link to Marylebone. From next month services will be cut by around 10 minutes to 36 minutes, slicing a couple of hours off the commute each week.
Simon Benfield, director of Hamnet Hayward, says the upgrade is causing excitement among the "Marlow and Beaconsfield crowd", who could pick up a four-bedroom Victorian villa in the town centre for £600,000 or a townhouse from around £800,000.
Thame has a well-thought of senior school, Lord Williams's School, rated "good" by Ofsted, but many parents opt for the nearby villages within Buckinghamshire, which runs a selective system (so they can try for the "outstanding" Aylesbury Grammar School). Benfield says the "A-stream" Bucks villages are Long Crendon, Duddington, Chearsley and Haddenham, but expect to pay about £1 million for a dream family house.
Average house prices along the M40
* Gerrards Cross: £852,000
* Beaconsfield: £751,000
* Farnham Common: £520,606
* Stoke Poges: £481,226
* Bourne: £480,272
* Amersham: £470,739
* Marlow: £466,681
* Chalfont St Peter: £456,000
* Henley: £421,000
* Princes Risborough: £403,000
* Wallington: £397,000
* Thame: £354,000
* Chinnor: £326,000
* Wallingford: £315,000