If I'm understanding correctly, what you need to do is shoot the
scene without the background music, edit the scene and then
lay in the music.

Or did you already shoot the scene with the music playing on
set and now what to match it?

Yes, ive shot the scene without music. Now ive got my dialogue levels sorted i want to add the music, but it wants to sound as though its coming from the living room/car and not just layed on top so to speak.

Any tips?

Many thanks

I've never tried removing a lot of the bass frequencies. You
should try that and let us know if it worked. It's something
that I'd like to try in the future.

I've had good luck with just adjusting the volume. I usually
have a dedicated audio person do my final mixes so I'm
not too familiar with the filters used,

Echoes should also help; when recording music they normally try hard to eliminate all echoes, so adding some with a similar delay to the environment they're in should make it sound more real and less like it's in a recording studio.

Some audio programs can do it automatically: you just tell them to add echoes like a small room and they'll do the calculations for you.

Cheers guys, ill try a tiny amount of room reverb and play with the volume

Are you trying to give the illusion that there is a speaker in the respective location playing the music? If so, you have to think about what your hypothetical sound source would be. If it's coming from a radio, I would think you should adjust the compression quality of the music playing (AM radio is very compressed, FM is quite compressed but not nearly as much as AM, etc.). Car speakers and CD players however would be much closer to full quality.

Playing with the mix levels is a good way to try and get things to blend better though. Try to find out specifically what may be causing the blending problems: if your dialogue is not as "full" sounding as your music, playing around with the EQ and taking out some lows/mids might not be a bad idea; if your music is completely "dead" in terms of reverb and your location was very live, then compensate with more/appropriate reverb, etc.

The same stuff everyone already said, but just trying to suggest some more specific things to think about.