Format the cells with the cells (say column a) as a number and the cells with the time as 'hh:mm'. So we then have, say, column A formatted as num, 2 dec, and column b as hh:mm. In column c row 1 (or wherever) use the formula '=A1/(B1*1440)'.
(Results then would be, A1 = '40.00' (i.e. £40), B1= '1:30' (one and a half hours) C1 would then be '0.44' (i.e. 44p per minute).