I haven't posted much before but I have been hovering around the TTC threads for a few months now wondering much the same as you Gangle! I am a City lawyer in a large corporate firm and also 5.5 PQE.
Absolutely agree that there is never a good time. However, I started my present job in early 2006 and you have to have been employed for 2 years by your EWC (estimated week of childbirth) to get the full maternity benefits. I am 31, but waiting another few months yet before really TTC (and not just playing Russian roulette with contraception!) Check out what benefits you are entitled to and when you reach to full maternity benefit, if you have only been there 10 months. Not very romantic, but it may help you cream off the most money.
i agree with Pollyanna and the others absolutely. It does depend on what your DP does. Mine works in finance and is overseas all the time with very odd hours, which is another reason why we hesitated, even though we are sure we want to TTC. He works away and disappears at short notice (e/g. note stuck to the fridge "Gone to Stockholm, back Friday") which is very tricky if you need practical back-up and support for a baby. Given the very long and highly unpredictable hours I work, we have talked and if he doesn't compromise his career too, then mine cannot continue at all. I have no family within hundreds of miles to help.
I have never met any City female lawyer who has been made up to partner after having kids. The nearest are two magic circle partners who got pregnant as soon as they were in the paddock and the firm would have been mental not to make them up because they'd be slapped with a cast iron claim for discrimination. They both had partners with flexable jobs and nannies. I know you said you didn't want to be a partner, but having a child probably will be a barrier to career progression (which is not a reason not to do it - I am really not being negative I promise, only realistic!)
The female lawyers who seem most fulfilled to me are the ones with a good work life balance - i.e. those who have gone in-house/become PSL's - and moved into an alternative role, where they can balance motherhood with a good job more easily and it offers flexibility which, let's face it, is in short supply with important PLC clients bellowing for everything to be done yesterday. In those jobs you are not ruled by the constant pressure to bill more and more hours and at the mercy of the unrealistic whims of several clients - they are the killers. It's not that you can't do full time City hours/travel and have kids, but the few people I know who try it are miserable and exhausted coping with everything. Even that Nicola Horlick person (is she known as Superwoman?) said in some article I read that she believed that you couldn't combine motherhood with being a City lawyer. In house is probably better than private practice because are employed by your client.
Hope I haven't offended anyone, as it's a case of horses for courses the way I see it, but there are few less forgiving careers around.