Hello Jen,
you can practice the Candle Exercise any time, of course! Everybody, course participant or not, is invited to do so!
Regarding the Inner Temple Meditation, everyone is welcome to do it, too, However we recommend that people mind the description (compare website) very well. If you do the meditation regularly and in doing so, get used to wrong inner images, e.g. if the magical well is not in the inner garden, but in the library, then the meditation and its symbols will not work properly anymore, and for some people it will be difficult to unlearn the wrong images.
Therefore we recommend regular Inner Temple meditations only for members, because they get comments on their meditations from experienced mentors. Therefore they are not so likely to get used to incongruous inner images.
"From the forums it seems that some students are doing so."
You mean the course forums? Then it is quite likely they are BOEL members. In the description of the introduction forum of the course you will find details on how to tell who is a member and who is not.
If you would like to do the Inner Temple meditation, you can use the Meditation and the Inner Temple forum in case you have any questions on your meditation realisations.
Hope this helps :-)
In Light
Andrea