Förstemann Squats

I seem to be fine in the longer distance races at the track, but I just dont have the build to compete in shorter races and sprints.

The build? Sy Lewis isn't exactly the hulk is he? power to weight ratio is what matters and as a slightly built person you already have an advantage.
What you actually mean is your % of muscle type, some people are genetically predisposed to having more of one type than the other, without complicating things and talking about slow/fast twitch, you may have more "endurance" muscles than "sprint" ones.

I really love keirins too, but find i'm just left for dead once the bell rings.... not through fatigue, but more due to the fact that I just don't have the power to keep up with the jump.
So, cardio is still OK but energy in the leg muscles has gone?

I have mostly been using the the squat machine, and leg press/extension machine, but it's too early to see any results as yet.... Also lots of stretching, and a bit of upper body type stuff. I normally do 3km on the rowing machine to warm up too.
What I'm asking is, are these types of exercise/machines going to be building the correct muscles in my legs, or am i just wasting my time? Should i just man up, and jump in with Creed-A-Likes, and see how much i can gurn whilst squatting in front of a massive mirror?.... I really can't see myself doing this and keeping a straight face!
machines will "build" muscle, provided you are following a hypertrophic program, but building mass alone isn't particularly useful for sprinting, it's strength you actually want to go for, and for that you need a strong core which is why sprinters use freeweights so the core is not neglected. Remember sprinting as about power which is strength (force) x speed. Strength training can and clearly does add muscle mass though, but it's "useful" muscle.

Also, would upping my training gear to around 92" instead of 86" help?
On the bike strength training is probably more useful to you at this stage, upping your gear like that for general training sessions won't help particularly, things like big gear standing starts, hill reps and flying/rolling efforts on the track/road will.

And finally, how often should I be going to the gym? Once the nights get longer, I hope to be training as many Saturdays, Sundays and Monday nights as i can make, and then racing on Wednesdays... I don't want to over do things. Would it be best to replace a weekend training session at the track, with a gym session?
You would need a coach to help work out your goals and form a program, otherwise you'll be mostly pissing in the wind listening to internet opinions and anecdotal evidence which won't help, none of this information is any good to you unless it's applied correctly. 99% of forum training "experts" can rattle off plenty about muscle groups and energy systems, but without understanding how to apply that information in order to benefit an individual's training it's of no particular use.

I dont want to turn into some massive freak like Forstermann, I just want to be able to put down some decent flying 200 times, and generally get a bit faster in short distance races.... (and maybe one day beat Jaygee in a sprint!)
Do you want to start match sprinting? because that's the reason for the 200, and sprint training can be very specific and very specialist, there are not many opportunities for sprinting at club level.
What would you class as a short distance race?