Is this a sensible way to do it?

Yep, that would work fine. That kind of scan type is known as an 'Infinity lock' - there's more on it here: One_on_One_Radar. That kind of radar algorithm will skip scans occasionally, so there are a few others on that page which are usually used on bots that aren't in severely limited codesize tournaments. Personally, I recommend the 'turn multiplier lock', it works perfectly and is quick and easy to implement.