First bike help!

Hello,

I’m looking to get a new bike for fitness purposes (an hour to 90 mins on roads and cycle paths going as fast as I can for as long as I can) and for family days out.

A friend of mine has lent me his Boardman CB 3XB Comp. I’ve loved riding it. 

Unfortunately, it’s no longer made, so I can:

a) buy the same bike off ebay for around £350

b) buy a Boardman 8.6 or 8.8 from Halfords

c) buy another model altogether 

I’ve looked online , reading reviews and scanning evans, tredz etc but there’s so much choice!

I’d appreciate any advice on good bikes for fitness/leisure at around £500. 

Thanks in advance.