Those guys don't know what they are talking about because they aren't adventurous, there are plenty of clean gals available for 100 or less. Krystil is older but she is awesome only 80 bucks, Monique is 80 bucks and really a lot of fun, there are plenty of younger babes as well like Sky, nice clean kinda kinky do your homework.
You are a wise man Hatrick. Those who suggest the OP just save up more money really aren't answering his question: He's on a tight budget. What can he get for $100? We all know if we had $300 or up to spend we could get a pretty good-looking, well-reviewed girl, from a nice-incall. (But even this isn't guaranteed, as sometimes I'd spend over $300 on an sp and wondered if I could've received the same service for half the price!)
So the challenge is what can be had, if anything, for $100? While I'm relatively new to pooning, I'm finding part of the fun (or "adventure" as Hatrick aptly puts it) of this hobby is trying to get the most out of your hard-earned dollars (whether it be $50 or $500). This often requires a ton of research and maybe even some word-of-mouth.
A quick search shows many Asian providers (likely aunties) providing FS at $100/h and Mandy 0570 (who is poorly reviewed and a WOT) out in Guildford at $100/h for FS and COF. As mentioned by others in this thread, there are much better options at the half hour or 15min rate.
This is not part of the OP's question, but I do believe however, there is a "sweet spot," around the 160 to 180 range where the quality of the girls (and I'm thinking mainly of Caucasian girls who give FS) in terms of service and looks increases dramatically and may provide just as good value as girls over the 200 (or even the 300) range. This is where your research is key and sometimes a bit of luck is needed to spot a "limited-time" only special. I'm thinking most recently of Dayna 3303 who gave an amazing special last month for $150/h. A week ago Selena 5878 and Alana 5878 were advertising evening specials of 160/h and 170/h respectively.
To the original poster then: For $100 you can't get much, perhaps a decent b&g including COF (again see suggestions given above by others), a nasty FS girl out in Surrey, or an auntie out in Richmond. With another red or so the options open up quite a bit. That said, don't feel you need to save up to $200 or $300 to get good value on your money. There are plenty of deals to be had below $200. But from my experience and research, if you want FS from a half-decent Caucasian girl (or a very decent Asian girl), you'll need at least $160 (as mentioned by scarface above) and a bit of homework and maybe some luck. Anything below that range for FS and your risks of getting ripped off start to increase.
S