IAN-UK

I'm pretty sure you can now. Otherwise it would be expensive, and a disincentive to the tourism they want to promote, to stop off in both direction if the transit version were no good. There again, multiple visits might be linked to business visits. The link above to the ROP has a pretty comprehensive list of visa types, but it's not well explained.

Multiple entry used to be available on the VOA, system, but only once you could satisfy them you were making frequent visits: at least that was more or less how it worked for me - at the whim of an immigration man, who said "why not?".