Rucsack, 35-50L
If you can afford it I would recommend two sets of base layers, that way you will have something dry the next day, it doesn't matter if your outer layers are still damp but it is nice to be dry for a few hours at least.
Think about wicking underwear. cotton will be uncomfortable and cold if wet.
1 warm fleece
1 good shell jacket
1 good shell trousers (side zips and straps are nice. Make sure you can move easily in them, high steps etc.)
1 pair of shell gloves
2 pairs of warm gloves that can be worn with the shell gloves as a layering system if it is very cold.
At least 2 pairs of good quality wool socks, eg. bridgedales or Thorlo. the warmest ones they have. ((that way you will have something dry the next day))
You need proper boots that can take crampons. Ask in a shop about these. I would recommend Scarpa or Meindl. You can rent boots if necessary.
You need a warm hat, I usually wear a rolled up ski mask, that way if it is very cold I can roll it down.
You should carry a small first aid kit. I would go to a pharmacy and buy the parts separately. the club will have their own sets but you can carry personal items. see here for an idea
www.traversesports.com/product.cfm?cid=178&bid=&pid=382 Water bottles. It will be very cold and the platypus hoses will freeze if you don't blow the water back into the bag. I used the platypus bladder but with a normal bottle top. Something to think about
Trekking poles can be very nice for the walk in and will save your knees, but then you have to carry them as soon as you reach the snow slopes and need your ice axe.
lip balm, and moisturiser unless you want the 'mountain man' look after a day or two.
Some suggest ski goggles but I never used these.
Obviously you need a save level of clothing, so you are not going to get hypothermia. Your boots are going to be critical. Cold and wet feet can ruin a trip. everything else is bearable. Make sure you have properly fitting mountaineering boots. Cheap boots will not insulate you enough from cold and could lead to blisters if they are ill fitting. Good socks are also extremely important if you want to have healthy feet at the end of the week.
I'm sure i left something out.
but hope i helped a little
oh I recommend looking at british online shops with the low sterling.
Cotswoldoutdoor.com has a great deal on icebreaker merino (lot better than plastic baselayers IMO)