Car not running properly

[Gingers4]

My car's doing the exact same , as it is in the dealer at the moment for a Brake judder they have advised changing the spark plug's to cure the flat spot. But for £ 250.00 for a set of plugs it sounds a bit steep if there's no guarantee of a fix.
Regarding the brake judder my car had new disc's & pads all round at 28 k , the newly fitted front pads were then replaced under parts warranty at 31 K as it was vibrating very badly if you so muched as looked at the pedal. These pads are now warped at 31,800 K and my dealer is investigating the problem. Possibly damaged hub.
Any thoughts folks ?