In the absence of any reply/comment to my starter post, I guess this topic is effectively closed. Before I actually close/delete it though, someone else might benefit from my experience of choosing a wholly mobile network service for all comm's.
I've now cancelled my land-line rental (my last 12 mth up-front land-line rental was equiv' to £16.49 p.m); I've also cancelled my associated discounted broadband (£2.99 p.m.) as well as my discounted SIM-only mob' monthly contract (£10.50): they amounted to £29.98 monthly.
Frantic efforts by Plusnet to keep me on-board would have produced a new 12 month land-line and b/b cost of £18 p.m. (!!!), but still with £10.50 p.m. to add for my mobile phone w 4GB of mobile data: total of £28.49 p.m.
For reference: the non-discounted rates for contract renewals (all contracts were coming to their end) would have been some £19 p.m for monthly line-rental landline, some £10.00 for b/band and the continuing £10.50 for unlimited voice/text with 4GB data = ~ £39.50.
I have cancelled all of above and now have a £15 p.m. inclusive (12 mth) mobile contract with Virgin Mobile that covers everything I need: 5,000 mins talk (well more than I need), unlimited texts (they obviously don't cost the provider much in terms of network usage) &, most importantly, 25GB data with roll-over of last month's unused data and a few other minor data perks.
[I'm not a major streamer of films/music/youtube etc so 25GB data allowance is good for me. Major data users , e.g. movie downloaders, would need much more data allowance - I have noted that the 50GB data combo package with Virgin would cost £25.]
Having checked my area coverage for mobile data etc, I looked for a provider using the EE network (cheapest deal was Virgin for me): other networks might be better for other areas obviously.
No, it's not quite as good as having a land-line/cable broadband connection where I presently live, BUT I'm definitely not grumbling about connectivity for just £15 p.m. for voice/text/internet. On an iPhone-generated hot-spot on my lower-ground floor (1 bar/4G reception) it is really very useable 99% of the time. If I crave something slightly snappier, I place phone in conservatory where it gets 2 bars/4G, which provides really quite responsive web data transfers for general web browsing.
(To note that some recent Youtube and Spotify streaming happened without any stutter what so ever!)
However, updating my iPhone's IOS has proved to be a pain: easiest to do while connected to a friend's WiFi connection to the web !!
Summary:
I have no financial connection with Virgin Mobile (other than paying them £15 p.m.) Reliance on a mobile network connection for internet purposes might not suit everyone: I'm happy though (where I live & for my web usage) and I am now saving min' of some £13.50 p.m compared to my previous discounted deals or, if you wish to consider a lazy person's saving, it would be a £24.50 p.m. saving on non-discounted rates! Either way, I'm smiling presently.