It seems that I've found an ideal solution for my nomadic painting lifestyle and I didn't have to look too far away - in fact, only as far as my excellent local games store, Firestorm Games. Yesterday I picked up a basic KR MultiCase and my paints have a new home that can easily travel around with me: around the house, to the in-laws, and to my new digs in Oxford (I'll be living there during the week from early October).
Here's how they fit:
Only a little modification required in order to fit the larger bottles - for these I simply slit down the dividers, taking care not to dislodge them completely, thereby creating larger sections. Simple stuff and really effective. Now I just need to demonstrate self control and not buy more paints...!