This doesn't fully answer your question, but is more of a side note - but don't be afraid to buy a 2nd hand 10 or 20 year old DSLR, with the kit lens, and a couple of lenses at higher zoom - for the cost of pretty much nothing, you can work out what does or doesn't work for you.

The weight hasn't changed much in any of the standard DSLR ones, so you can go in a modern camera shop and pick up one of those to get an idea of the weight you're after - then just find an older one from the same series 2nd hand in cash converters or eBay or whatever.

They might have comparatively lower pixel resolution than these days, but even a prosumer DSLR from ~2010 was good enough to produce "international exhibition" quality photos.

Spend your other £950 once you realise what your current kit is lacking.

In terms of brands, it's just your normal camera brands (Nikon, Canon EOS etc) - but if you were to look at the website of "Wildlife Photographer of the Year" and look at all the winning entrants, the additional info will tell you exactly what camera they used - which may be a useful guide as to what they're using at the top end.

You don't need the same as what they're using at the top end, by the way. As said, a 20 year old entry-level DSLR will absolutely work fine!