I've never heard of a driver who wants to go back to something less accurate after running on RTK for a while?
Probably because he'd feel like a bit of a dick for buying 2 unlocks and a radio module @ C. £4500, and not using them.
RTX is more than sufficient unless doing precision veg work. It also costs only £220 if bought direct from Trimble, or £250 through an agent
To the OP, I wouldn't bother with an RTK base, at least not until you have more seat time with the cheaper alternatives.