www.ultimatehandyman.co.uk

How much money can you save?

Depends on lots of factors.
How many panels, what direction they face, how much sunshine you get.

Real question to get answered is what will be the repay period for the investment to start providing profit for you !

Advantages cheaper fuel and feel good factor
disadvantages
cost to instal and maintain
possible damage to roof
possible devaluation off property
possible increased repair costs for roof
https://www.gov.uk/feed-in-tariffs

Thanks a lot for the advice.

I researched some articles in google and found this one about Solar Panels Metal Roof - Blog About Solar Energy | Websolarguide

Your link does not work, but even so, your link (i figured where it goes) is of no use since in the UK 99.7% of houses do not have a metal roof.