Animated video for startup

At Meetzapp we want to help users meet interesting people nearby whilst doing things they really enjoy (ie run in the park, drinks, going to a gallery, etc.).

We are looking to build a 60-90 second animated video which will allow us to introduce our company in a cheerful, interesting and engaging way.

These are the requirements:
- 60-90 second video
- Animated video
- British voiceover
- Script will be provided but as I do not have experience creating videos I will expect your advice and modifications
- Suggestions to make video viral will be expected

Some videos I've see which I like and would like to reference are:
- Wemeet: http://vimeo.com/76128954 (to the point)
- Tinderella: http://www.youtube.com/watch?v=bLoRPielarA (good graphics)
- Dumb ways to die: http://www.youtube.com/watch?v=IJNR2EpS0jw (catchy)

I know budget is not high but it's what we can work on right now. We will be producing more videos in a short period of time so a job well done will mean potential future work.

Please get back to me with:
- Estimate of how much it will take to build, and time to deliver
- Step by step process of how you will build and what you expect from me
- Price
- Detail of what will be included within the budget

Waiting to read your proposals.

Regards,

Ricardo