I had my baby at Lewisham two years ago and found that the labour ward itself was fine, staff very professional, and I got on well with my midwife. When I needed it, the doctors were there very quickly. I was in the 'home from home' room for most of my labour which I would recommend. A hospital tour first is definitely worth it. As with any hospital, the experience you have will also depend on who is on duty when you are there and whether you get on with the midwife allocated to you - and that is just down to luck really.
But from my personal experience, (and from what I have heard from others I have spoken to recently), don't expect too much from the postnatal ward. Take some snacks with you or get a visitor to bring some in, as the hospital food isn't great (and you'll probably be starving!); if you need something or have any worries, be prepared to ask; and the midwives and nurses aren't particularly friendly - they are busy and have many other mums and babies to deal with, and they can perhaps forget that whilst they are used to dealing with babies all day, for you its a very new and unsettling experience! Help with breastfeeding can be sporadic and different nurses can give different advice about the best way to feed. So do read up as much as you can beforehand, and hopefully you won't be in the hospital too long anyway.
I don't mean this to be a negative reason not to have your baby at Lewisham, as I certainly don't regret it, just something to be forewarned about.
By the way, I don't know if people on here are aware that the Maternity Unit (and some other units) at Lewisham may possibly be closed under recent proposals to change health provision in south east London.