I'll admit, a few people like diesels but it's a pretty niche Market. (And I do have a soft spot for Deltics!)
I'd question your age before making a full reply Nathan, but I feel this needs a quantitive (I think that's the correct word) reply from someone who has "been there, done that, got the T.shirt".
I started 'train spotting' at the grand old age of 9 years of age, on Donnie ( Doncaster ) station, I was lucky enough to catch the change over from steam to diesel, as well as seeing the first of the 'Deltic' services (2 tone green in them days).
Yes, I have a soft spot for Deltics just as you have, so much so, that I was among the very first of the members of the 'Deltic Preservation Society', this was a few years before any purchase was made, when the hard work needed to be done, just to raise the cash for the first bid.
However, as much as steam is so much a never to be forgotten part of the heritage of British Rail & it's forerunners, the diesels of the 1960's up until the ousting of the Deltics by the HST in the 1980's, is a very varied & interesting era, you should not dismiss it without a second thought if you have any interest in the heritage of our countries railways.
They were glorious days to those that actually lived through them.