Is it easy to navigate round any sections that are closed off,
It is easy – you can just use fire roads, but the sections that are closed (all of the north loop and the upper section of the south) account for about 70% of the red grade trail. There's no point in navigating around it, as there's nothing to reach – it's not a section here and a section there that's shut, if you know what I mean. With the blue and lower sections of the south loop, there's an hours leisurely paced riding.
There are other trails there, but unless you've already worked that out by using a map, you won't find them.
Do the Borrowdale Bash or some riding around Skiddaw, or 20 mins south is Grasmere, from where you can access a wealth of excellent rideable trails e.g this month's mbr route