I'll pop up and say: dump the landline! With good reason and evidence of my own experiences. My landline provider, TalkTalk, were fine till they decided to put DLM on ADSL lines which screwed up the speed. Went from a quite stable 2.9Mb to 0.6Mb where it has never recovered and paraphrasing from their official speed test "...because the speed is higher than than when we first connected you (0.5Mb) and we've actually increased the speed at the exchange over the years, we're not going to help you get it back. How would you like fibre that may be faster but we're not guaranteeing it?". At the same time I discovered 4G appeared in my area during a power cut....
So back to the question: I've been running off 4G for the last year and I just about hit the 50GB monthly limit on my package. Bear in mind that I usually do 2-3 hours of Netflix at SD per day, I work from home and the connection is active for 8 hours daytime per working week (mostly VPN/remote desktop with encryption going), does the usual app updates on the phone and computer and I browse the internet during the Netflix sessions. So can be actively using 4G from about 9am to midnight some days and to be honest, I was surprised that I never hit 50GB so you may be surprised how little you actually need.
I have an unlocked Huawei Wifi Pro with the ethernet port which is worth seeking out if you have a small network setup though annoyingly, you can't switch off the wifi. The other main advantage is that I can take it with me on work trips without needing to use hotel wifi and less hassle when using a Chromecast. There are other options for a fixed router available which I looked at but the Huawei is that good that its difficult to justify replacing it at this point in time.
Also, the reliability has been far better than the landline. Only twice has it dropped the network and one of those times was weather related. Compared to the landline, its outstanding reliability given I work from home.
Also I went with Vodafone rather than o2 because a) they had 30 days rolling which o2 didn't have at the time b) o2 was oddly slower on the upload speed than VF yet they share the same mast! I did a test of both networks which was actually worth doing even if it costs initially. The other networks are hopeless where I live so were never in consideration though I would suggest trying the other networks as it may be better where you are at a cheaper cost.
As I still have a landline and want to keep hold of that number for various reasons though it will be predominatly mobile for calls, I'm going to try out VOIP (SIP) this week over 4G and see how that works out before I finally start the process to terminate the landline leaving minimal cost for keeping the landline.
My mobile phone data plan is 6GB and I don't use all of that either so some scope to go cheaper if I need to.
BTW, I tend to get between 10 and 20Mb depending on time of day. More than enough speed!
