The main IBM scheme does give you a list to choose from although there's very little limitation - anything from a 1.0D Pacific rim shopping mobile to a 911 (if you want to fork out £1500 a month!). Terms are 24, 36 or 48 months, the longer the lease the lower the cost (generally).
The figure seems a bit low for the main scheme so I'm guessing it's either the Essential Car User scheme or more likely the Market Scheme. If it's the latter then you should have access to the full list from the lease companies, £250 a month is 1.4 Polo or Civic territory.