New Light Fittings Not Working

[Markoldbarn10]

Hi all.
I have recently replaced two ceiling lights in the lounge (both on the same circuit with one switch) and they don't work.
I have tried the following so far:
1) checked and re-checked they have been fitted correctly and there are no lose wires in the terminals.
2) tried the lights elsewhere in the house to see if they worked, which they did.
3) tried a plain ceiling rose, flex and bulb in place of the new light fittings. Circuit did not work.
4) changed the switch to see if the original was faulty. Still no lights in the lounge.

The house is nearly ten years old,so there is no really old wiring. All I have done is replace light fittings. No drilling, as I have used the existing holes in the ceiling for the fixings so therefore not drilling through any wires. All the other lights downstairs on the same MCB are working.

I am baffled and frustrated that a simple task has caused me so much of a problem. I really don't know what to do next, as my knowledge of electrics is limited. Can anyone suggest any ideas for finding what the fault may be to save me spending money on getting an electrician out to sort something that appears to be a fairly basic issue?

Thanks for your help.