Thanks for all the supportive comments, its much appreciated. In answer to some of your questions.
Jimbo325ci: The roof tiles are individually cut from 0.5mm evergreen plastic card 5mm square and laid down in much the same way as you'd do a real roof, its a slow procedure but it gives good results. I normally hand paint it with acrylic paints. I got the idea from reading one of Allan Downes articles, check out his stuff to see how a real master works!
Dave: The windows were cut from 0.5mm evergreen sheet using a silver bullet die cutter machine that I bought a couple of months ago. It was a pricey enough investment that I was hemming and hawing about for a while but under a bit of advise from Richie who has one himself I bit the bullet (excuse the pun) and bought one with no regrets. The process I use involves drawing up the shapes in autocad, normally a window will have 3-4 different layers that are cut and laminated on top of each other to build up to the right depth.
Josefstadt: The texture process I use for the brick work is me taking a photo of the actual building facade and cleaning it up in photoshop and if I can't get access to a particular part of the building I find a similar looking wall either locally or online (http://www.cgtextures.com is a good one). As I have the building in question drawn up in autocad I simply export the drawing as a pdf file into photoshop and layer over to insure everything lines up as it should. I print it out at as high a resolution as I can to be glued onto each facade. I print out an elevation of the building from autocad and using the point of a compass I mark the corner of each window, door and wall edge for cutting out. Everything lines up perfectly. The only draw back of using this process is it can look a bit flat so I try to break up the space using features made of plastic as much as I can. The real focus of any building on a layout is the roof and its here I spend the most time on.
I hope this answers some of your questions, if you've any more I'd be only too happy to answer.