They were monster engines. You might want to try obtaining the Hornby "N15" cylinder block (ask Peter's Spares, for example, if they've got one in stock) and using it to replace the 8F one. That would make the chassis look more convincing.

Hi Ivan.

Yes, I had considered that as Peter's Spares do advertise the N15 cylinders periodically. However, I was going to try filing down the sides of the Stanier ones first and use a little Milliput to build up the valve chests a bit to resemble the G16/H16 cylinder style more closely. If that fails then I will invest in the N15 cylinders. Thanks for that suggestion though.  

I like Peter's Spares and have bought stuff off them before but I tend to build up an order for multiple items as the postage to Australia tends to be bit on the dear side for one item only.

Exactly, what you want is something that nicely replicates the Urie cylinder appearance, which was pretty flat-sided.