If you don't have the required subjects for the course and you aren't taking them, you will be immediately rejected.
Most courses do not use the UCAS Tariff and certainly neither UCL nor Cambridge use it.
Again it's really unclear what grades you have now, if any, and what you are retaking and when, if at all. Basically you are not providing any information to provide any specific advice so all that stands is the general information I gave above.
If you aren't an international student you will not be accepted to the UCL preparatory certificate so unless you qualify as an international fee paying student and have ~£50000 to pay for tuition fees, you should stop considering that option.
Again, actually read the requirements and entry criteria for the courses you are considering applying to. You are just randomly picking things based on, apparently, prestige, without a single thought about what the requirements are as far as I can tell. This is the fastest way to ensure you get zero offers.