I am goin to service my 1999 1.8 mondeo soon and was jus wondering if there would be any difference in putting better spark plugs in??

For everyday driving it's probably not worth paying a lot for spark plugs and you can start paying silly money - £10-15 per plug

I use NGK or Bosch (preferably NGK).

You'd be better spending the extra money on some good quality oil, like Castrol Magnatec or GTX

I am goin to service my 1999 1.8 mondeo soon and was jus wondering if there would be any difference in putting better spark plugs in??

They'll probably last a little longer before they start going off. if you do a low annual mileage, this probably won't be an issue to you, as you'll probably change them anyway before things get too bad. Also, if you have, eg, cold starting problems, better spark plugs might make some difference...or they might not.

@L666JER

I use NGK or Bosch (preferably NGK).

I've never had any problems with Bosch, but some people do complain about them, so, in general, I'd prefer NGK. Also used Denso, and have nothing bad to say about them, either (if that falls short of a rave review, that's deliberate; they are spark plugs, and you don't notice the things unless something is wrong).

@L666JER

Castrol Magnatec or GTX

Castrol GTX Magnatec over plain GTX, imnvho. Or, anything that meets the -C spec over the -B (the last time I looked, anyway, the plain GTX only met -B)