A pack of 20 downlights for £20 - A pound a pop. What a classy install. What tat.
If you have habitable rooms above, you NEED fire rated fittings to keep the integrity of the plasterboard ceiling - The plasterboard ceiling being there not only to look pretty, but to prevent the spread of fire to rooms above, giving emergency services time to arrive and rescue you.
I hope all your connections are contained in a joint box of some sort - I would guess these cheap lights are not designed to have cables looped into and out of them. I hope you maintained the continuity of your earths too.
This qty of fittings also would more than likely have required a new circuit. I bet you did not consider this.
No decent sparky would go within a mile of those cheapy tacky fittings. They would of quoted for decent BRANDED ones, and would of allowed a good whole day+ for the works. I would be looking at around £600 for this, or £1000 for 10yr guaranteed LED versions.
If your attitude had come across while I was looking at the job, I would of doubled the price, not wishing to get the job.