Dear Nick,
You choose for the Canon EOS 350D body...that's fine...I hope your hands are not too big?

Rather a small (but a very good price/quality) body!.
Can you tell us your budget (+/-) for the lens you want to buy?
Please note that everything is also a bit personal linked.
Canon has good lenses. Sigma also (they "cooperate" together so...).
Everybody (don't take it too serious) will prefer his/her lenses due to his/her hapiness, experience etc.
For me, the 75-300 is a good lens to start with. Ok it has CA (Chromatic Aberration, well spelled?), ok its autofocus is not of the quickest, ok its not weather sealed. But like for example in aviation...you get what you have payed for. (not all the times but ok those are exceptions)
Off course one must keep in mind that there are some very good post image editors with "less good equippment" but with very good image processing skills. (which can make the difference off course in the Digital Photography World)
For me Canon (body) + Canon (lens, teleconvertor...) is still my favourite choice.
The L lenses of Canon are thé elite in the world of photography. (not all of them) But as fellow spotter Andries already said, its not made for your budget (we presume that). You have cheaper L lenses. For me (personal) an L lens like the 28-300 is too expensive. For that price you have an L 70-200 and L 100-400...
Please tell us your budget for the lens in EUR, Nick, I think we can help you more then.
Btw, nice pics Andries.
Warm regards,
Tommy