Brilliant, thank you.

Just one query, please. If I have read your reply correctly, it seems that both routers need to be close enough together to have a patch lead which joins them directly together and not through the switch. Is this correct?

Ideally connect them directly. If you need to go via the central point, just use a coupler or add another £20 switch there for the purpose or change your central switch for one that supports VLANs.

That is great. Many thanks.