The amount of possible combinations is 60*60*60*60*60, which is 777,600,000. There is an equal chance of getting it on the first go as there is getting it on the last go - which is 1 in 777,600,000. After trying half of that many times - 388,800,000 - there will be a 50% chance that they will have cracked the code and a 50% chance that they will not have cracked the code. So the average amount of tries it will take is 388,800,000.
If they get fined £1 million 388,800,000 times this will mean a total lose of £388,800,000,000,000. When they crack the safe they will get £100,000,000,000,000. Now take this money away from their losses and you get £288,800,000,000,000, which is the average amount of money that they will lose.