Hi Darren,
As I frequently say here and may even have done so in one of my replies to you, there's a big difference between what a court would find to be infringing and what a zealous company might consider to be infringement. The latter, if they have deep pockets, might indulge in threatening tactics right up to the door of the court, before backing down. They can do this because, unlike with registered designs and trade marks, there is nothing actionable about making unwarranted threats in respect of copyright infringement.
So turning to your example, I think there is very little chance that "All you need is Love" would be found to infringe. It's an everyday use of English and was so before Lennon/McCartney wrote their song, and even though it is the title of the song, I think the amount used would fail the 'substantial amount' test. There is also the new exception for quotation which I am sure could be advanced here. However none of that guarantees that Apple Records or whoever owns the rights to the lyrics won't see things differently.
Incidentally the words have been registered as an EU trade mark although not in a class which would affect your badges.
