Someone Somewhere wrote:
One thing to consider, is that whilst Oxford isn't particularly great
traffic wise, if your wife was to commute there and you lived in London
(or its outskirts), at least she'd be going against the majority of the
flow of traffic for a lot of the journey.

A friend of mine did that - living in Victoria (so just round the corner
from Victoria Coach Station) and taking the buses to Oxford a few days a
week. It wasn't too bad apparently - but I dread to think what the rent for
living in Victoria was!

Another option of living halfway is to consider the Chiltern route -
Kidlington, Bicester, High Wycombe, etc, possibly even Banbury. I don't
know how that works out in terms of times and costs.

Also worth working out what you're pay in rent/mortgage for each place: pay
1Kpa extra on the season ticket but save 2K on rent?

OP: Where in London is your job? That could make a big difference. For
instance, if you work in Canary Wharf you might want to be near Crossrail.
That either implies Reading or getting the X90 or Oxford Tube to Marble Arch
and walking to Bond St for Crossrail.

Theo