IF you have the child seat sensor (indicator on interior light)
Then you need a Britax base with built in transponder to shut off the airbag.
No other safe option.. kids safest in the back anyway.
ISOFIX, unlikely to be in your car, was a factory fit option.
Which leaves you with the standard seat belt retainers.
Some of these clip round a base, you then click the car seat in and out at will
Some clip round the actual child seat and are a bit more of a faff.
You may find you want a towel or something like a gripliner between the seat and childseat to improve the 'fit'
And one other personal thing....The lift in and out car seats are ok...for the 1st couple of months. Then baby gets heavier, and they are quite awkward.
Yes they are convienint to lift in and out, esp if baby is asleep etc....
If I had my time again, not sure I would bother, and just put in a more fixed solution - group 0,1,2 car seat and just move the baby. such as these :
http://www.mothercare.com/combinations-car-seats/b/44451031?intid=catlp_carseats_puff_2