Have Virgin given any indication when they are looking to roll out FTTC?
It sounds like a Leased Line (sometimes referred to as FTTP) may be best in this instance. A Leased Line which is a dedicated fibre connection may be more expensive but will be a much more reliable solution (typically with a 99.99% uptime). In the event of downtime, the best industry-leading resolution time is currently a 30minute response and a 4 hour fix.
How much would 4G cost? Depending on the cost of this, it may be worth looking at a leased line.
With the leased line you could look to share it out between neighbours and segregate the bandwidth (i.e. 4 residents, each get a fully synchronous 25Mbps connection, pay 1/4 of the line each). This tends to be a popular choice when people are unable to get FTTC in the area.
Is your dad's business a limited company? I know some organisations who provide leased lines will only deal with limited companies as the cost can be significant (depending on supplier, the existing infrastructure etc).
If you need any further help, feel free to drop me a message.