I'm Daniel and will do what I can to assist you. Please do not rate me until we are done, and feel free to ask as much as you need.
Just so I understand the situation, a former employer unfairly dismissed you. you have then taken them to a tribunal and they (former employer) have sent a letter to you via your solicitor that has been doctored by your former employers general manager?
ok. right, what is it about the letter that makes you suspect that it has been doctored
what I would do in this situation is write a brief letter to your solicitor explaining this, and ask him/her to write to your former employer asking for a copy of the original letter sent to you via email.
In which case, you need to proceed with the hearing, and when you have your chance in court, explain that you have received partial correspondence from previous employer and wish for it to be investigated.
not without access to your original email account it was sent to.