Could somebody tell me spark plug gap, just fitted new plugs and car is running a bit lumpy ?

usually if you buy the correct plug you dont need to set the gaps as many are preset

As Chris says plugs should be twin ground electrode platinum-tipped and they must not be adjusted.

I have the GS300 sport and this is listed in my hand-book and told by the garage on no account fit adjustable plugs.

If you have fitted the correct ones and the car is running lumpy you may have damaged one of the coil packs that goes on top of the plugs (common fault as they get a bit fragile with age.