Sexuality of any kind has always been repressed in the UK. That situation then allows humour to work which uses "double entendre". I'm sure M&S chose the name specifically to gain some media coverage. If there was a backlash they could still claim it was an innocent reference to something heart shaped, produced for Valentine's day. Nudge, nudge, wink, wink.
I think what M&S are doing is not dissimilar to what Dr Bateman is doing (discussion on other thread).
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