Sorry, I don't know the exchange rate or the average prices for baby things in the UK, so my answer may be useless - but I know what I appreciated in the first months after my baby was born.
You can make a few meals to put in the freezer, so mum doesn't need to cook all the time (which helps dad too, if he is a lazy bum or a bad cook or has any inconveniently timed work trips).
A nursing cover is also nice. You can probably find a nice one with a strap for a reasonable price. Or if you are at all handy, you can get some fabric from a sewing shop, and sew one up yourself (it's mostly straight lines, so easy to do - you just need access to a sewing machine).
You can also offer to come by for tea, and help with whatever she needs help with. Could be transfering baby's laundry from washer to dryer, or helping with a few dishes. The house work can become overwhelming in the first few months. Any help at all, will be appreciated.