Just for reference (and yes, quality is rubbish) but I took these a few years ago, which demonstrates the identical body likeness of 24/1 and the first twenty five, 25/0's. 24.119 on HA, 25.001 on ED and 25.025 on PO.
A summary - from memory - of class 24 & 25 external design differences:
Class 24:
D5000-5113 (24 001-113): Round-topped cab roof, disc headcode indicators, under cab air horns and bodyside air grilles.
D5114-5133 (24 114-132): Roof-mounted headcode boxes, under cab air horns, bodyside air grilles and token exchanger recess on left hand side of cab.
D5133-5150 (24 133-150): As above, but without token exchanger recess.
Class 25:
D5151-5175 (25 001-025): Identical to D5133-5151.
D5176-5232 (25 026-082) & D7568-7597 (25 218-247): Cab roof-mounted air horns either side of Headcode boxes and larger windscreens.
D5233-5299 (25 083-149), D7500-7567 (25 150-217) & D7598-7677 (25 248-327): As above, but with no corridor connection doors, full-sized centre windscreen and air inlet grilles moved from bodysides to roof cantrail level (as in class 26 & 27).
In addition, ISTR that a small batch of the later Derby-built locos (D7598-7606?) were delivered to the Scottish Region with cabside token exchanger recesses.
Further details can be found at
www.derbysulzers.com