Another to recommend hiring a proper hospital grade pump, or seeing if your hospital will lend you one for free. I hired a Medela symphony for the first 2 months at £40 a month. Was very quiet and efficient, well worth it. It has a sort of two phase action which mimics baby sucking patterns. I mainly used it to express for the 2-3am feed as in the early days I couldn't hack being up for ages trying to tandem bf or juggle between the two in the middle of the night, but was told it is important to stimulate your milk supply at this time of day so didn't want to just give formula. Did this for about 5-6 weeks till bf was established and got the hang of tandem. I never seemed to find the time to pump at other times of day. You don't know what your own feeding issues will be or what coping strategies you will need until you get there though.
If you do think you may want to hire one, find out where you can get one and keep the phone number in your hospital bag so you can arrange easily at the time.
If not I have heard the Medela swing is a good one, though have never used personally.
If you do end up pumping a good pump is essential but I'm not sure whether it's worth buying in advance.
Before I had my twins most recommendations for buying were for a Medela Swing or an Ameda Lactaline or others recommended I hired a hospital grade pump (most of which are likely to be Medela or Ameda pumps). I checked where I could buy/hire quickly and then because of circumstances (my DTS had tongue tie and didn't latch until it was cut) I opted to buy an Ameda Lactaline when the DTs were about 4 days old. It's served me well - for three weeks I pumped every feed for DTS and then from about 10 weeks I pumped an evening bottle for DTS. However, my DTD is a bottle refuser so for her the pump has been useless!
So, my advice would be to buy or hire a good one but maybe wait until DTs arrive. If they are in SCBU you should be able to use hospital pumps and again you'll have a chance to decide what to do next. My twins weren't in SCBU but I got a chance to try an Ameda pump in hospital and because it suited me fine that helped influence what I ended up buying.
I am expecting twins in Oct and by all accounts, a breast pump seems to be a vital purchase for some. Which did you like and why? I tried a breast pump with DS1 (Tommee Tipee) but hated the noise and slow pace, found it a faff and sold it, threw out the bottles and ebf. Is there a fast one? I'll want a double. Best, most efficient brand/make? May be handy in case any special care required in the early days or do I pump at the hospital? Advice appreciated.