They are great little enignes imo.
Very good round town especially, you dont seem to need to change gear as often as in most cars.
Out of town they are fine, they like to sit at 60 more than 70+ and they do seem very good on fuel at 60MPG.
Mine usually averages about 38-43MPG but thats nearly all town work, doing short runs.
The 1.0 engines are usually very strong and as long as they are looked after they are very reliable. But i wont mention the issues with mine, but they were a one off, so im told
Anyway thats a really good price i think and very low mileage. Is it a 1.0 base, or 1.0S?
The 'S' model is the one to go for.
Lunalupi mentioned rust on the rear wheel arches, this can be an issue with MK1 arosa but the one you are looking at will be a mki2 so it shouldnt rust, they are galvanised, and have a 12 year anti perforation warranty on them.
I carnt really think of any common problems really.
But make sure its had a cambelt change, its every 40K or 4 years, i would risk going over that recommended time.