Hi Tom
Welcome to the forum

If you have booked an Upper flight that comes with the limo transfer then you can utilise the Drive-thru check-in, more details
here on the VS website, but basically you are driven in the limo to the Check-in area (you'll spot it easily when you arrive) and 'processed' there, you'll be relieved of luggage, given your boarding pass, and you can head straight for the Clubhouse.
If you didnt get an Upper flight with a limo (one of the Z fares for instance) you will have to use the normal check-in inside the Terminal, but i wouldnt worry too much as check-in will likely be very swift.
The LGW Clubhouse is very nice indeed and has the usual wealth of complimentary food, drinks, snacks and of course your V Touch treatment. Furthe info on the LGW CH (including contact details for treatment booking) can be found
here on the VS website.
I hope that helps? You might want to do a search (using the search function at the top of the page) to look for recent trip reports on the BGI route to get an idea on whats instore
Have a great flight!