I can enthusiastically vouch for the R7, absolutely perfect for what OP is after. The others below it (R10 etc) would be great too if the budget truly is tight, but personally I think the 7 is worth finding the extra for.
As the other commenter suggested, the 100-500 is going to blow the entire budget by itself a couple of times over. BUT the 100-400 f5.6-8 is a great lens. It's not hard to find for around 1k AUD (~500 GBP) brand new, so I'd imagine a bit less than that used.
Not sure if you'd be able to get both within the provided budget, but that's an extremely capable combo.