Just book it as follows using the multi-city tool.



Then buy a normal one-way VCE-LON (LGW might be cheaper and maybe even more convenient for central London locations).

Then simply click through for the results you want. If you have specific dates in mind, post them and I can look to see if some flights will be cheaper than others. All other things being equal, avoid the 787 in economy, and consider whether you want to route through London at all.