Can I access airport lounges upon international arrival at Gatwick (LGW)?

Do you have a business or First Class ticket? If so you should be able to access your airline's lounge.

The Gatwick Airport website lists the Regus Express Lounge in the South Terminal as an arrivals Lounge. I have no personal experience with Gatwick, but this might be a place to start with your inquires.

In case already not clear, you won't be able to access any departure lounges airside before immigration but any arrival lounge you are eligible for afterwards.

Ask your airline. It depends on your type of ticket and whether your airline's lounge serves as both a departure and arrivals lounge (or whether the airline has a separate arrivals lounge).

Thanks for everyone's input. Appreciate it very much.

I have a lounge access via AMEX Platinum Card and Priority Pass. The question is if you can get to the lounges after clearing the UK border check.

Most of the lounges are "Airside", for departing passengers after they have been through security and exited the UK.
Not accessible from "landside", which is where you will be after landing and clearing UK border immigration.

My previous answer listed the one lounge on the Gatwick Airport website that is listed as an arrival lounge. It is not on the list for priority pass.

I researched this extensively and short answer is that AMEX & PP will not help you here. Your options for a shower and some rest are the Regus Lounge (20 pounds the shower, 30 with lounge access) or the Yotel.