Buck: yes it is, but stuart cameron has worked it out on a monthly basis. You won't have to find the excess mileage money until the end of the term, but knowing it's monthly cost upfront will help you compare how much the car will really cost you for your stint as keeper.
These National Vehicle Solutions terms are decent when compared to buying - you're talking an average £320pm for 10k miles per annum x 24 months to lease.
To buy: Through solutions, putting down £2900 deposit (to get you to £27k purchase price after discount), 24 months terms @10k miles per annum comes back at 23 x £403.76 (equivalent to 24 x £386.94). You'll be £65 a month better off leasing, unless you get £1560 more than GFV as p/x against the next one (Possible, £1000 is more likely).