I almost used those guys cause I live in Reading and work in Slough but it was easier for me to use a place nearer work, in Maidenhead and get the train from there to work. I left it with them first thing and collected it at lunchtime. Not sure how long it actually took them tho suspect a while.
I used
http://www.autoasylum.co.uk. They did a very good job and it was about £280 I think for the rear and rear side windows. Not that cheap but well worth it.
I think they said they wouldn't do the front ones as they'd then be illegal but I didn't want them done anyway. The owner had two of his own cars there so I got to see what the tints looked like plus he had samples he could hold over your window. Knew his stuff. I was going to get either medium or dark and he suggested dark on rear and medium on sides as the rear would look thru to the clear windscreen so by using that combination the rear and side ones would actually end up looking more similar.
My only mistake was to get in the back of my car after it was done to see what they looked like from inside, except had child locks on the doors. Doh