Okay. So you will probably want a highly directional microphone (or Shotgun). It does not pick up too much sound from your surroundings and focuses on the actor without having to be 1 inch from his mouth. I can give you some recommendations, but the links will mostly be to a German store (this is the one I know). They will probably deliver to the UK, but I don't know at what price.
In your price range, I would recommend to get a
Rode NTG-2. Is has a brilliant signal to noise ratio and you can power it with a battery if you ever want to plug it into the miniplug of your camera without phantom power. The lower frequencies are a little louder, but that will make voices sound very natural in an outside environment. I did some test on this one and some other microphones and even uploaded the "finale" to
youtube, if you want to check out how it sounds.
I would definitely recommend you to get some additional gear, to be able to use the equipment properly. Things you definitely need (if you don't have them already) are:
- A
Deadcat windscreen
- A reliable
XLR cable (don't go with the really cheap ones)
- Closed
headphones with a mini-plug
What you might want in addition, but don't necessarily need or can build yourself:
- A
camera cable to connect the mic to your T3i
- A
boompole (those are surprisingly expensive and easy to build yourself)
- A
shockmount to mount the mic on the pole (can also be built)
You definitely want a dedicated sound guy at the shoot. Someone who does nothing but take care of the sound. Strap the H4n around his neck and have him wear the closed headphones at all times. He has to point the shotgun mic at the actor's mouth from just outside the camera frame. If you point it from above (that's how it's done most times), you get a very clear and crispy sound with little background noise. If you point it from below (sometimes done outdoors or for practical reasons), the actors' voices will sound deeper and more "chesty". If you have more than one actor in the scene, the sound guy will have to point the mic to whoever is talking before they actually start. This takes some practice.
Last but not least: What you will get with this kind of mic is a very clear sound with very little background. This will be almost unnatural (since the ambient noise is missing). Be sure to always get a "clean plate" of your ambient sound. Have everyone be quiet for 2 minutes and record the room tone with your H4n's internal mics. You can put this over all your sound in editing or fill pauses with it. But you'll hate yourself if you forgot to get it.
Good luck and have fun.