Apparently LR supply their pads with a fixing kit containing anti squeal pads.

The ones from ARE I've just had fitted definitely don't!

Any ideas where I can source?

That's right If they are genuine they are manufactured with a hard man made material stuck to the back.
OE and pattern don't have the pad but it's not needed just a dab of copper grease on the back and sides where the pad locates will do.
Some vehicles have anti-squeal shims but thats is something else.