After a consultation, the Government has decided not to allow big brands to sue producers who use copycat packaging directly unless, as has always been the case, the copycat is actually 'passing itself off' as the big brand. I think this is the right result - we live in a branded environment so big producers will always influence the style of smaller producers. I also suspect most consumers know they're buying a lookalike product and prefer the lower price point. Outlawing copycat packing regardless of consumers being mislead would reduce choice and push up prices. This article also nicely points out why this is the right thing for brands themselves in the long term.
If a brand is strong enough to connect on an emotional level with the consumer, then no matter where range extensions may lead the brand, its equity will remain intact and protected from copycatting.