Yes hornby use loksound. Their sound files are different to all you will be able to buy though. There should be enough room inside the loco body for the decoder (8 pin socket is at the front of the chassis, near the funnel), but there is very little room for a speaker in the loco too. There is, as said already, plenty of room in the tender, but that means running the speaker wires from the decoder to the tender. Not impossible, but would take a little skill and patience. There was an excellent article by Paul Chetter in Hornby magazine a couple of years ago doing just that (and some more). I can't remember which edition it was and my copy is packed away for a house move so I can't dig it out, but maybe someone else could help here. There is a range of 'sugar cube' speakers which are remarkably small with great sounds for the size which may be possible to squeeze into the loco body. Loksound decoders come with a speaker, but you may want to switch it for a better quality one, just make sure whatever you use has the right ohms rating for the decoder. Good luck.