I am looking for a recommendation for an easy fell walk (we are staying in Borrowdale) that would be suitable for someone with serious balance issues - so no scrambling or difficult terrain. Steepness and length are not a problem.
Might be difficult to suggest suitable walks, as it would really depend on your exact interpretation/meaning of "Easy Fell", "serious balance issues" and "difficult terrain".
If walking on the typical Lakeland fell-side track, (which might be rough/rocky/loose-gravelly/very narrow between peat-hags, etc., etc,), is within capability, then there are quite a few walks that should be fine for you. - Most of which might reasonably be assessed by reading the relevant route-guide, looking at some good quality mapping (such as WalkLakes GPS mapping!), and in particular, satellite mapping zoomed in as far as practicable to get as much terrain detail as possible.
If walking on such paths isn't a problem, then, assuming you have means to get to the start points, (and noting your mention that walk-length and steepness aren't issues), walks like the two below shouldn't present too much of a problem; -
Dale Head from Honister Pass.
This walk is quite short and starts at about 350m in altitude, saving quite a bit of ascent, However, on the right day (weather-wise), the views from Dale Head are among the best in Lakeland!
And, the walk could easily be extended as a ridge-walk, taking in Hindscarth and Robinson, giving more opportunity for superb views towards the fells beyond Buttermere - Haystacks/Pillar/High Crag/ High Stile/Red Pike/Grasmoor etc. etc.
The only slight downside might be (in order to avoid lengthy ascent at the end of the walk), the need to return to Honister Pass via the same path from Dale Head, so making the walk somewhat linear rather than a circular route.
Another possibility might be something like Great End from Seathwaite.
Walking up the Grains Gill path to Esk Hause, and then following the "Calf Cove" track towards Broad Crag, but veering off towards Great End before the extensive boulder field on Broad Crag is reached.
Returning from Great End to Esk Hause, you could then take in Sprinkling Tarn, before deciding whether to return to Seathwaite via the Grains Gill track, or to continue on to Styhead Tarn, returning to Seathwaite via the Styhead Gill track.
Do note though, that some parts of the tracks walked would definitely be classed as rough/rocky upland fell type tracks.
Thank you so much that's really useful.
I have made a note to look into Dale Head & Great End. I also read on another forum that Latrigg might be a good option. Do you have any thoughts on how this would compare?
(Sorry if I was a bit unclear - by difficult terrain I just mean trying to minimise walking on scree or anything where we would have to be picking out any kind of route. Just looking for a simple path really)
For context - we did this walk earlier in the year and this was too challenging:
I suspect, (if your earlier "Rosthwaite Round" walk was too challenging), that the two walks I mentioned would almost certainly be too challenging, as they go into the higher fells, and both cross areas where the paths are rough or jagged.
(And they also have sections where paths may become somewhat indistinct. Particularly so if the weather deteriorates and if you aren't confident with map navigation).
Latrigg is a very easy fell, and if started from the Underscar car-parking area, is really no more than a ten minute stroll on a grassy track. (Nevertheless, it does offer superb views over the Vale of Keswick, across towards Borrowdale and the Coledale fells).
Your best option for finding something suitable would be to use the "Walks-Finder", and browse through the "Gentle" and "Easy" walks, here on the WalkLakes website. There are numerous walks described there that should be within your capabilities.
If you aren't very confident about navigating, I'd suggest sticking to lower level fells like Latrigg, or trying some of the "around the lake" type walks with very obvious paths, such as around Rydal Water (maybe taking in Rydal Cave).
I really wouldn't like to encourage you to go anywhere amongst the higher fells if you aren't confident with navigation. Weather conditions can and do change very quickly.
If you have access to one, then the use of a suitable GPS device "should", in theory, keep you on track as they give you the opportunity to reverse your walk if needs be using the "track-back" facility. - But note that GPS units have been known to fail!
I wouldn't recommend using a mobile phone mapping app though. Despite the fact that countless people do use them, for me, and without paper map and compass as backup, (and the skills to use them!), mobile phones (and even GPS units if it comes right down to it), are simply not 100% reliable as sole navigation aids.