Need help please after recent iPlayer changes
I don't think it'll do any harm,, but I thought I'd just check.

If I uninstall the older version and install the new one, it won't affect the downloaded recordings will it?
No. Also, when you run the uninstaller you'll be prompted with "Remove User Preferences, PVR Searches, Presets and Recording History?". I assume you haven't made any settings that you want to keep. If so, answer Yes. If in doubt, answer No.