Hi Gazza
Some charge the same in as out, some charge time and a half, and some charge double,
Take you pick, its what you think you can get in your own area, but don't forget the advice from the guy's about orniments, it takes time to remove and replace them,
I charge one and a half times the amount unless they have internal doors then I price Accordingly, if you get a customer who ums and arrs then tell them you have to use a different insurance for inside work and this cost you more.
Take extra care on the outside work first, because once inside you tend to spot all the bits on the outside you may have missed, and you have to keep going out side to remove them.
I wish I had this advice when I first started it would have saved lots of extra work and time.
all the advice the guy's have given you so far, remember it for the future its all very good advice and will save you time, money, and embarrassment. GOOD LUCK!