alb, 100/30 is a very fair price and is the top price among the uk bookmakers.
Firstly if you require prices on most european sports from twelve or more bookmakers, even if its to compare with north american books, may I suggest
www.oddschecker.com . You will find it easy to navigate.
This game will be a tight affair between the best two form sides in division one. Sheffield United's confidence must be sky high at present after beating Liverpool last week. The blades are unbeaten in the last 13 winning 10. Aside from beating Liverpool, they have beaten Leeds and Sunderland amongst tose ten wins. Portsmouth have lost only to Man Utd and Leicester in their last 17. A draw might satisfy both sides, but the longer the game remains tight the more chance Sheffield United will have as Portsmouth go in search of a winning opportunity.
If I was playing this game I would consider playing the Asian line with Sheffield United +0.5 . Therefore you will also have the draw on your side. I notice that this is generally 10/11 (-110), but 21/20 (+105) is available from a few books.