I got a copy of the new 5-8 for 7 and barely opened it. They are forever saying we covered this elsewhere, rattling on about ancient history (only needed for 8) and saying we don't understand the question. And they are pricey and verbose. OK, so that's a bit one-sided but for 3 I'd say it's unnecessary (though may be proved wrong after November!)
and we did 1/2 without it....though can't say we passed yet! My partner reckons you could almost pass 1 from learning the Thornes catalogue