the best place to get downlights are rexel in myaree or the beacon lighting right next door for 11.95 for white ones or 13.95 for silver ones. in all my time of doing downlights these seem to work very well.

the key to their lifetime is moving all insulation well away from the downlight and the transformer because they produce a crap load of heat.

as for a gpo id say your lookingat between 80-100 dollars per gpo, installed