del1962 said:
Be prepared to get very wet
Seriouely you could look at the Scottish section in Simon Warren's books 100 and another 100 climbs for some suggestions of climbs (not routes)
Not sure about bike hire
Not much in there unfortunately.
If you are up North then the Belach Na Ba route is the one to do, the closest you'll get to an Alpine climb in the UK. It's on my list for this summer. Otherwise you'll find that the roads are very quiet as you head North and great for riding, where exactly are you going? If you're in Inverness then head west for Applecross and the Belach Na Ba road, Isle of Skye and Ullapool. The road from Ullapool to Durness is fantastic. Make sure you have a working phone and emergency food with you, there can be long stretches with no-one around. If you're around Glasgow let me know, those are my training roads. Over to the east you'll find the Cairngorms with a few nice roads, Aviemore to Elgin is good.
As del says, be prepared for the weather. It's humid so a light rain shell of even just a gilet will probably be fine if you feel the cold, but make sure you have something.
You can certainly rent bikes at the Tiso outdoor adventure centre in Glasgow so I'm sure you must be able to elsewhere. If you let me know where you will be I can give a couple of places a ring for you.