Of course any aspiring commercial pilot will grab with both hands any opportunity to fly a twin. To purchase an hour costs hundreds of pounds. To be able to fly a twin and record that in your logbook for no or little cost is worth hundreds of pounds per hour in experience.
Plus it is exciting and it is interesting. It adds to your range of abilities and skills as a pilot. Flying a twin engine aircraft after flying only singles feels like a big step up on the ladder. Which it is.
If anyone offers you the chance to fly a twin even if it is just a few circuits post maintenance or maybe a short navigation trip to a nearby airfield then you should not hesitate to grab that opportunity. Occasionally twins do need to be moved over greater distances and such ferry trips can allow a good few hours to be logged for free. Just remember that you cannot accept payment unless you hold a Commercial license. A bottle of wine for your trouble if not unknown though.
Cheers
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