I can't imagine local law enforcement in any country giving this the time of day. You think the average police officer knows about bitcoin, asic miners, etc? Technically this is a civil matter. You paid for something you didn't get. If you were to do this in the US you would have to hire an attorney to sue "john doe", and in the process get a judge to compel the ISP to release the name of this individual. Expensive and time consuming. Who knows what the process is in the UK or wherever this person lives.
It can be civil, criminal, or both - one does not exclude the other.
US law enforcement can and does investigate internet fraud (typically as "wire fraud"). "Bitcoin" is just a payment method in this context and "miner" is just a product.