Anyone fitted one of theses before I need help please

Have just seen the old post you replied to. Do you need to remove a split hose from your car to replace or to reuse? If you are replacing it you can just cut it with a craft knife, along it's length. That will release it from the barbed fittings.

Getting a replacement on successfully without leaks or damage is another question. Soak the ends in boiling water to soften them up first. Alternatively get some replacement rubber hose of suitable bore (maybe 3/8") and a couple if hose clamps (careful not to overtighten).