Hi mate, plenty of info on here so probably worth doing a search.
With the Ph1's, you'll probably have to be patient, as the older these cars get, the more dogs you'll find. Personally, I'd set your mileage limit to 80,000 (10k a year is pretty reasonable) and don't let mileage dictate your purchasing habits - higher mileage could well just mean that the owner does lots of motorway miles. The number of previous owners being high is more telling IMO, but then these cars tend to do the rounds fairly frequently due to their cheap, cheerful and fun nature. Expect to find a really good condition one for £3500, and anything under £3k is usually going to be a little ropey.
These cars NEED to have had at least one cambelt change in their lives and should really be getting near a second, so if it's not had its second yet, bargain a bit.
Don't worry if they have little dings on the doors or stone chips on the front, the paint and panels are soft and flimsy. The standard Renault exhaust is also rubbish, so if it hasn't been replaced in the life of the car, expect it to need replacing soon! The best bet is to go aftermarket.
With the interior, the steering wheels always go crap so don't worry if it looks bad, and the silver grab handles on the doors also lose their lacquer and can look poor. The seats are generally pretty good, you'll find the leather starts to crack but the alcantara is pretty tough wearing. Mine had 75k on the clock and the driver's side was only just starting to bobble, the rest of the seats were perfect.
Hope this helps...