Hi Rhys,
It is clear that one does not need to ordain to attain a magga pala. There are many suttas on these aspects. During the Buddha’s time there were lay people who had attained upto the anagami stage and did not have the urge to ordain. There were some who ordained after becoming a sotapanna, some of them attained arahanthship and others may not have even attained sakadagami level. There were others who ordained without being sotapanna, and from this group some attained soatapanna level while others did not.
As Vince has mentioned the monastic life can help in ones practice. But it may not be for everyone, at least not until they reach some level.
Personally i think its much more important to attain the sotapanna stage, which can be done as a lay person, rather than running and getting ordained. This is for me personally, but I dont want to dissuade anyone from ordaining as their ways may be different from mine and it may even actually help them.