Thank you all so much, I honestly can't say how grateful I am for your posts.
I'll try to answer each thing raised. Tongue tie - the paediatrician checked for this and said he didn't have it. It seems that all my equipment works ok as I can express about 120ml per feed in 20 minutes (10 on each boob) and at the moment DS is only on about 70ml per feed calculated by birth weight.
He vigerously sucks at a finger or the bottle, just not at my nipple, which he looks at like it's some bizarre foreign object 
At the moment I am just using a borrowed Avent pump which is working ok, but I can imagine I would need more in the future. To be honest, if I could just get to a couple of months I would probably be happy. DS has already had formula anyway as he had really low blood sugar at birth due to my gestational diabetes, and needed to be fed asap.
Again, I don't have anything against formula per se, it's just that I have all this lovely milk and a hungry growing baby and I want the two to go together!
The lactation consultant in the hospital was useless, just kept repeating "make sure he takes a full mouthful of BREAST" even though it was obviously not working.
We've done loads of skin to skin, tried latching with a nipple shield, latching during pumping, everything basically. Even the lovely paediatrician that we had, who fully supported breastfeeding said it would be worth us looking into other options.
So, you have all reassured me though and I'll continue doing what I'm doing. Luckily DS seems to be into a vague routine of 4 hourly feeds during the day, increasing to 3 hourly from about 7pm until 4am and then back to 4 again, and at the moment I seem to be able to pump enough to stay ahead.
Oh and strikeup thank you so much for the "fridge trick" that makes perfect sense - it's actually the washing and sterilising that takes the time as I am so careful about it, so if I can cut that down a bit that would really help.
I'll have a look at that forum as well. It's hard to find info about this - even my books don't say how much you should be feeding a breastfed baby if you're expressing, which makes sense as "normal" breastfeeders I guess don't need to worry about amounts!
Thanks so much again.