Speed improvements:
Return solutioncount instead of using global: it's a bit faster.
Assuming we never want to print the answer, remove the coin count.
Use some variables to avoid repeating lookups and computations.
Deduct directly from amount instead of multiplying.
Short-circuit computing 1p coins: we can always use pence to finish it off.
Time it using 100 repetitions to remove jitter.
Rename to something more reasonable (remove .py).