La Barbiera do a UK made hard cake at 60g in Fresh Lemon and Sweet Orange. I also remember DR Harris Arlington as being citrus forward in the opening. P&B Albion, as already mentioned, definitely has a good whack of grapefruit going on - great soap. I finished a tub years ago.
Still, I think Signature Soaps is your best bet. Fabulous soap and plenty of Citrus options. They also do a pure lime if that appeals - it certainly does to me.
Seaside Soao & Skincare do a great pure lemon which smells very natural and not at all synthetic. Again, it’s excellent soap that I’ve tried. Their Frankincense, Lavender & Bergamot is a real wow scent.