Don't touch the Hornby (ex Lima ) Deltic with a bargepole.
Its a centimeter or so too short, the bogies are to HO scale not OO (they were originally planning to make it in HO and switched to OO part way through).
A schoolfriend had one many years ago - I remember Lima's take on Brunswick green was pretty well fluorescent
Somewhere along the line the tooling has been modified to feature the Wipac cluster headlights acquired by one preserved example for mainline running a few years ago.
And it's only available in a train set.
(Some of us had rather hoped the Lima Deltic had been towed out to sea and sunk by naval gunfire. No such luck)
The Bachmann Deltic is a vastly superior model , the right length, with the right bogies and with a proper modern mechanism . Unfortunately it fell foul of a couple of prominent rivet counters and isn't in the current Bachmann catalogue
The rivet counters objected to the lack of a seam on the nose of the Peak. Otherwise it's fine.
The Hornby 8F is a good model with a good mechanism, if you want steam. The Bachmann 9F is superb
Both the Bachmann 66 and Hornby 60 are excellent
The Bachmann 20 was a wonderful bargain, though they've now fitted a 21 pin socket , and reduced the flywheel size . The 21 pin DCC socket isn'[t an issue if you run on DC. However if you've got birthday present funds you may want something more ambitious
If you like plain workaday engines a Bachmann WD suggests itself.
And if the Southern is your thing, Q1s may be had at bargain prices
