Les Ward
I would fit fire rated dimmable LED fittings. The loft insulation should be moved away from around and over the fittings to extend their life. The fittings can be placed close to joists as there is no fire risk from heat generation, unlike halogen lighting. This work is subject to building control (as making holes in a ceiling affects it's resistance to fire) so use a Part P registered electrician for this work. LED lights use much less power than halogens so the possible extra cost of the LED fittings can be recovered over time.