Hi,
I would recommend you do this job yourself and save a lot of money. It's no more difficult than wiring a plug, just always make sure you isolate your power before you work ( Turn off the trip that provides light to the rooms in question). Take your time and mark off where you want spots positioned, measuring off walls and other fixed points to get square. Buy your fittings, transformers etc in an Electrical Suppliers. They will provide you with the exact drill fitting you need for the light fittings you buy giving you a nice neat hole. This is an easy DIY job done in a day(made easier by the access to your attic). I have done all the above myself and it's genuinely easy.
Good Luck,
Maddad.