Easy way to check fuel pump failure, take off the oil cap and smell - if it smells STRONGLY of fuel then that's it. But TBH, as has been said by Dan, oil level increase can only be one thing and that is fuel in the oil and the fuel pump is the main culprit. The oil will be so thin that it cannot maintain the pressure needed to keep all the parts from hitting themselves.
Could also be cam follower failure, which in turn wears down the end of the fuel pump etc - won't know until it's removed and inspected..
Don't drive it to the garage, get them to pick it up with a trailer. Don't let them drive it away, it may well be ok for the drive to the garage but it's not worth the risk of killing the engine.