I want to make a temporary answerphone which records MP3s
I use twilio, very easy, very fun.
An artistic project will encourage users to ring a number and leave a voice-mail on an automated service. These voice-mails will be collected and edited into a half-hour radio show. 
I want to make a temporary system (with as little as possible programming) which will:

Allow me to establish a public telephone number (preferably in the UK)
Allow members of the public to call in and receive a short pre-recorded message
Leave a message of their own after the beep.
At the end of the project I'd like to be able to download and convert the recorded audio into a format that I can edit with a free audio-editor. 

I do not mind paying to use a service if it means I can get away with doing less programming work. Also it's got to be reliable because once recorded it will be impossible to re-record the audio clips. Once set up the whole thing will run for at most 2 weeks.
I'm a python programmer with some basic familiarity with VOIP, however I'd prefer not to set up a big complex system like Asterisk since I do not ever intend to use the system again once the project is over. Whatever I do has to be really simple and disposable. Also I have access to Linux and FreeBSD systems (no Windows, sorry).
Thanks!