Here's a couple in your area mate, dont know of there work but best to ring around and see some examples of there work.
And yeah could do that, might work out abit more expensive not having it all done at once, but if your not sure it might be best to just do the rear's and see.
http://www.exclusivetints.co.uk/
or
Smart Tints
6, Debdale Avenue,
Lyppard Woodgreen,
Worcester,
Worcestershire
WR4 0RP
01905 619154
07841198288