Fresh from an Alteryx training session a few days ago (thank you @jamielaird), I thought I'd try these challenges. Let's see how far I can go.
Here's my solution to the first challenge. I went on replicating range string for each customer (via formula) and then summarising it before matching it with the range data. My solution needs to be modified to future proof it when the post code range changes, but at least it works for the current solution.