Sorry to hear of the problem, however it can be sorted quickly and easily given that the dispute is covered by an Ombudsman scheme.
No lawyer is required for this as it is designed for consumers who are in dispute with an energy supplier.
To avail of the scheme you have to first make a complaint to the energy company, wait for their final response and then go to the Ombudsman.
In the meantime you should dispute the bill. They should not take any enforcement action for the duration of the complaint investigation.
If they do present you with a large estimated bill, you must make a formal complaint and if that does not resolve the matter ask them for a "deadlock letter", which is a letter giving their final response.
If the complaint is for high or estimated meter readings, a template letter can be found here which maybe useful :
The complaint to SSE can be made here which has a form to complete online : https://sse.co.uk/about-us/sse-and-you/making-a-complaint
Once you have the deadlock letter the next step would be to escalate this to the Energy Ombudsman - they will investigate and liaise with the energy company which would hopefully result in a reduction, or a cancellation with no bill to pay.
The Ombudsman can order the energy company to make a financial award for inconvenience if they have acted poorly.
The service is covered by the Consumer Rights Act 2015 so you have a right to expect a reasonable service which is carried out with care and skill - if you do not receive this then the regulator will step in.
Once you have SSE's final response, you can complain to the Energy Ombudsman by email here: *****@******.***
Or via their website here: www.ombudsman-services.org/energy-complaint.html
If they sued (which I highly doubt if you make the complaint now and then go to the Ombudsman) then the court will send you a claim form and a response pack - you must fill in the response pack to confirm you want to defend the claim and then return it to the court. If you ignored it or delayed then the claimant can request default judgment (which means a county court judgment, or a CCJ).