I have a TW house and my back garden looks like this - I was wondering if this is normal or whether I have a case to complain? 
It's very boggy and the site manager says it's normal 

Hi Rob
Soil is something we check on our snagging inspection. Couple of things to bear in mind with water logging. NHBC guidelines stipulate that water cannot be pooling withing 3 metres of any rear doors e.g. patios, and this includes your flag paving. They stipulate this is at least 1 hour after rainfall.
The NHBC have technical guidelines to state that soil should not be contaminated and 100mm of topsoil. We find that developers rarely provide such topsoil and that in fact it is heavy clay with building rubble. I can see not only is it clumpy and heavy in clay, it also has weeds so its good evidence.
Our best advise if you are not having any joy with your site manager is raise a complaint through their customer care dept. TW are a big company so have an infrastructure that will hopefully help in such matters. But to answer your question, we would certainly raise a lawn in this condition and you are right to be concerned.... any turf thrown on top will at best be boggy and at worst it'll not survive. We hope this helped