Is it worth getting two separate lines to get decent bandwidth on one for work and general use on the other?
Absolutely! Even when you’re guaranteed decent speeds i.e. 40Mbps down and 10Mbps up, working from home can soon see your bandwidth being eaten up by other things i.e. if you’re living with others that are working, as well as if you’re living with children or young adults whom may be online learning or gaming etc.
A dedicated second broadband specifically for work will lessen the impact - you can even program some routers to manage the traffic on an IP or traffic basis to “load-balance” across both lines, so you can govern which line gets used for what device/IP, or just evenly distribute all traffic across both lines.
The DrayTek Vigor 2800 series routers have multi-WAN capabilities that allow for more than one broadband connection to be plugged in at any one time, with just the requirement for an additional separate modem if both lines are DSL/phone line type broadbands. Some models will even allow for backup 4G dongle or better still, have SIM slots built in.
I hope this helps.