To make it easy for you, you're looking for £1m/month of revenues to begin the exercise...and we'll take it on from there.
Let's try and put that into perspective. The charges for PIK are as follows:
Landing Fees: £4.62 per tonne or part thereof
Parking Fees: £0.27 per tonne per hour or part thereof
Passenger Charge (International): £10.89 per departing passenger
Security: £2.15 per departing passenger, £0.50 per checked bag.
So using those figures, lets calculate the revenue from a single 737-800 at full load, each passenger carrying 1 bag, staying for 30 minutes. (MTOW 66 tonnes, 189 passengers)
Landing Charge: £304.92
Parking Fees: £17.82
Passenger Charge: £2058
Security: £406.35 + £94.50
So that's a total revenue of £2881.59 from a single 737-800 round trip flight, or £86,447 for 30 flights a month.
So to make £1m a month in extra revenue, you will need to add 12 extra 737-800 flights per day. Unfortunately though, almost no-one will pay list prices, the staff will not work for free, and various other companies will probably want a cut of that revenue, so in reality you will be looking at a lot more than that to break even.
As you can see, the main source of revenue is from Passenger Charges. A 747-400F (MTOW = 397 tonnes) would bring in just £1834, although there will be additional freight handling charges.
Also it's worth mentioning that PIKs landing fees are a fair bit lower than most others, Leeds Bradford charges £14.33 per tonne, Newcastle £6.90.