Can anyone advise me on how to remove the back screw on the PRD (Triton Ivory 3)? I've tried with an angled screw driver but the access is still too tight. Also tried loosening other parts but does not help with the access. Seems a pity to have to replace the entire shower just because I can't access and replace this one small part. Bit of a design fault to me given that this is usually the part that goes wrong. Thanks