Another possibility to consider is using compositing for the master shot. Lock off the camera, light your performer and have her do her scene. Then, while she's off on a break, move your lights to various positions and highlight spots around the church, shooting a few seconds of each position with the still locked-off camera. In the edit suite you can extract stills from each of the lighting positions and create a composite of the entire church using soft masks, then mask-in the spot where the girl is doing her scene.

Essentially it's a modern alternative to a matte painting.

see now im pretty comfortable with compositing so that is a very interesting approach i will look into and thanks Bill, i totally agree and believe even tho i dont have the best i can still get close to what im after if i work it out right. Im sure i can get my hands on a few work lights

I've done some more research into fogging my scene to add to the look and i came across 'diffusion in a can' Diffusion In A Can 8oz. aka Fog-in-a-can. SHIPS BY GROUND ONLY. but they only ship via the ground and Im in the UK. does anyone know of a UK/international vendor of the product? thanks

Fog machines are easy and inexpensive to rent from many places. The space you describe is way too big for fog in a can. I will echo the earlier sentiment that there is often an aversion to renting gear these days--if your project is worth shooting, it's worth spending a little on to make it look right. Small tungsten is dirt cheap to rent just about anywhere (even if it has to be privately owned kit).

Without location stills, it's very hard to make suggestions that are entirely appropriate; maybe you can put them on a site and link to them if you are having trouble uploading them here.

You did mention that there are doors off the hallway--placing lights in the rooms off the hall allows you to light subjects as they move down the hall quite easily, and with nice edginess as desired.