Good luck, that's not a lot of info to go on, Greater London is massive so without a town or borough and a range of dates you've got your work cut out.
I would stick to the free sites rather than the pay sites.
Clarke family tree, and connecting branches and roots, from Hampshire, UK to the Titanic + beyond. We have links for the name CLARKE obviously, so many others, see the whole list. If you have a connection to our family tree, or would like to put out a request for tree stuff assistance, email pauly @ this domain I will try to help... This site is also home to my blog, with links to all the things I like. All about me, my wife + our beautiful boys... Also the usual things, work, TV, parkrun, ect ect, and links to my fun projects.