Hi and welcome.
I've only just purchased my first 240z with my dad (arriving next week) and recently been in a similar position to you. Lots of friendly and very knowledgeable people on here imo.
What sort of car are you looking for? UK, USA, JDM spec? Do you have any requirements in mind? age, colour, standard or modified? and what sort of budget did you have in mind?
All of the above makes it easier for everyone to know what sort of specification your after. I ended up purchasing a 1971 USA car as it fitted all of my requirements and seemed to be the largest most accessible market for 240Z's with prices generally lower, albeit the exchange rate has changed that somewhat given recent political affairs. West coast cars generally tend to have less rust etc. UK and JDM cars will be more expensive however have the added bonus of being RHD and usually higher specification over US market cars. Don't be scared of sourcing your own car from overseas and importing, the process has been relatively straight forward for me so far. There's also a few very helpful US forums if you chose to go down that path on that side of the pond.
All the above said, most on here will be far more knowledgeable than me and hopefully along shortly to help out.
Where abouts in London are you? I'm in Surrey, working in London and wondering the same. Would be great to meet some other owners and kick some tyres