Just wondering if anyone has one of the rubberised coatings on their flat roof, opininions if you do, would be very welcome.

Possibly not what you are talking about but I have used ISOFLEX liquid rubber on a cracked concrete roof (an air raid shelter!), a couple of thick layers will last many years. Its not cheap but I didn't want to have to repeat the job and I found it relatively easy to work with.

http://www.thompsonsweatherproofing.co.uk/roof-and-gutter/isoflex-liquid-rubber/

B&Q, Screwfix, Wickes etc sell it, Screwfix is about £10 cheaper for the large tin http://www.screwfix.com/search?search=isoflex

I had my garage and carport (one flat roof)
covered in sheet EDPM synthetic rubber.

I had already had it redone with bitumen
and felt but this soon leaked and I was
always fixing it. Felt/bitumen becomes
brittle and cracks but rubber remains
flexible as the roof expands and contracts.

The rubber sheet comes in one piece. They
remove any sharp points and lay a polyester
cushion material. The rubber sheet is laid
on top and fed up adjoining walls by six inches
and secured around the edges by grouting
into the wall or with clips over the roof edge.

They fix and shape the sheet into the drain.

They then lay about four inches of gravel on
top to weigh down the rubber sheet.

This worked fine for me for several years
and was still fine when I sold the house.

The manufacturers gave a 25 year warranty
against failure due to the elements. I was
always careful to only go onto it in soft
soled shoes to avoid punctures.

It has to be the right grade of synthetic
rubber to withstand UV and heat from the sun.