But the VS A330-300 PE seats are a couple of inches wider than the Delta PE seats.
The other consideration is whether you want to fly into MAN or LHR. Depending on where you will be going in England, MAN can be a lot easier and more manageable airport than LHR. From MAN you can get trains directly to a number of other cities without having to change in the Manchester central station.
If you are Delta PM or DM it is worth returning from LHR just to be able to use the VS Clubhouse, regardless of which airline you are flying.