Agreed. That one of the most important points!!!
You cant use one or the other alone!
Also if you need any advice, ask the workers at B&Q. I know they dont have the best customer service but usually the do have 1 or 2 staff that know the electrics :)
No standard dimmer switches should work with GU10 lamps. However it might be useful using a low-load dimmer switch.
The best way would be to use a "silent intelligent trailing edge dimmer"
These will work with GLS and GU10 bulbs.
Also its best to use a branded make of switches compare to...