If you have actual Matrix Biolage Hydrating Conditioning Balm in the UK, you might try checking around and see if you can find a knock-off version. That's what I always use after henna, and it's great - no proteins.

If Lustrasilk conditioners are available there, they're supposed to be great, too, although I'm not sure if it's totally protein-free. In the US, it seems to be available mostly at beauty supply stores, usually in their ethnic section. I just got some of the Shea/Mango/Cholesterol myself but haven't actually used it yet. A 20 oz. jar of it was only $2.49 at Sally's Beauty Supply here - a jar more than twice as large as the Boot's pink curl cream 250 ml. jar, if you're familiar with that.
2C/3A/3B - mod. CG, med. to fine, normal to low porosity/normal elasticity

Current Main Rotation: MG217 medicated, GTTT or Aim2Health 'poos as scalp needs, YTCarrots or Elucence cond., Spiral Solutions Protein Trtmt & Deeply Decadent Cond., CJCCCC reg or lite, KCCC, AO Mandarin Magic, Giovanni LA Hold Hair Spritz + lots more, sporadically

HG Method: Super Soaker + Smasters-ing, brief upside down diffusing then clips or clamps & air dry. Blend gray w/henna glosses