We've been talking about this recently. There are quite a few porro lovers (or at least porro likers!) around here. Me, FrankD and Steve C come to mind but there are plenty of others.
For around $100:
Bushnell Legend 8x42 porro is a very good buy in this range.
The Leupold Yosemite 6x30 or 8x30 are good buys (though I rather prefer the 6x of these).
Just to confuse matters with the same name ... the Eagle Optics Raptor 10x42 (not the Audubon Raptor 10x42) is a nice 10x bin. See the Binocular Bargains thread for the link to the Eagle Optics eBay store. But you may not want 10x to start.
Celestron Ultima DX 8x32 if you can get it is still a very good bin ($75 last time I saw it and much better than the Audubon Raptor).
Nikon Action Extreme 7x35 (the waterproof one with good eye relief) though I've heard nice comments about the view through the non-waterproof (and short eye relief) Nikon Action 7x35.
Search for the Audbon Family thread I started there are a couple of comments on the Raptor there. Basically it's a nice bin but it has stray light problems in "normal" use which were too much for me at least.
You should be able to have a very good time with a $110 or less porro.
Hunt around the site (search works well!) and you'll see quite a few comments. They start to make more sense after a while
PS: after writing all of that I see you are in the UK ... that makes it more difficult to get some models I mention above (with my US-centric view).
Plus opens you up to some different brands ... we need some UK residents to chip in on Opticron and other UK OEM options.
Hawke also have a good porro for under £100 that has been mentioned on the board.