Brushed Aluminium Stirrup Mains Spotlight For GU10 Lamps

Can LED bulbs be used in this light?
Yes, if you look at the spare bulbs section in the products specification there are a few LED GU10 bulbs listed

I`d like to put this on a wall. Does the bracket turn down 90 degrees and does the base swivel?
Yes, this fitting offers 90º tilt and 350º rotation.

I would like to know if these spotlights will easily replace the old fashioned flush ceiling downlights. The diameter of the hole left in the ceiling is 2.5inches (63.5 mm). I see the mount base is 54 mm in diameter. Can it sit inside the old white ring fitment which is 54mm where it allows for the bulb head? Or how is this spotlight supposed to be fitted. I have never done this before and would like to attempt without cost of electrician.
The diameter of the base is too small to be installed over the existing 63.5mm hole. While it may fit inside the existing 54mm ring it`s not something we`d recommend as securing them in there wouldn`t be easy and would require modification of the product. The normal procedure would be to remove the old lights completely, plaster over these holes then install the lights into the new plaster.

What are the dimensions of the mounting base?
The base is 54mm in diameter.

Can you tell me if this spotlight is bright enough to put in a kitchen which is orange in colour?
We`d need more information to give a real answer. First colours; white reflects around 70% of light and magnolia reflects around 50% of light so your orange finish is likely to reflect on 20-30% of the light hitting it. However if you have enough direct light the reflected light matters less - but indirect or reflected light is what makes a space light and airy. If you want you kitchen to be nice space you`ll benefit from direct light and indirect light (reflected or "bounced" off the ceiling). So spots using reflector lamps may bot be the best solution.