Made it to the Hilton from T5. Thanks to C-W-S and others in this thread for the advice.

Some more pointers for others doing this:

When you get off at Starlight bus stop in the direction that the bus came and not in the direction that it’s going which is towards the Premier Inn.

A few yards down and you’ll see a small service road on the opposite side with a red square sign saying STOP HILTON. Walk down that road and go straight through pass all the creates of good and stuff.

You’ll then come to the bottom of the car park. Go up the 4/5 steps onto the main car park area. Then right next to you will be a parking pay machine and with it 4 flights of steps.

Once at the stop of the steps you are in front of the Hilton entrance.

The steps are not good if you have lots of luggage.

Regarding the lounge, the food offering is pretty poor for a Hilton. The lounge is nice though.