pursuing guarantor for rent arrears, use my solicitor or is it simple to do myself?

I have a court order for rent arrears of £3874.86 plus costs of £276.75 for ex tenant. Now his mother was guarantor and has been in to pay £2000 of this amount off with a letter to say that she will not be paying a penny more because her son has told her (a lie) that he stopped paying rent due to the boiler being not serviced and not working! :(shake): My solicitor has been dealing with the issue up until now, and as you can guess most of the money has been what he has charged me anyway! He has written back to her enclosing a copy of the gas certificate that proves this is incorrect and the boiler was in fact working and as 14 days have now passed without her response he is going to pursue her for the remainder of the arrears but this is going to cost me even more (is it worth it?) I wonder if it is now simple enough for me to pursue her myself for the remainder via small claims court or something? Do I need to obtain a third party debt order? she also asks that we deduct the deposit from the amount owed... is this correct? Can i also pursue her for the solicitors fees on top?

I am also chasing the letting agent for compensation as it turns out the tenant was an employee of theirs and they did not do any background checks on him despite charging me the full finders fee! They have been hiding many issues from me and failed to do property checks on him, he was growing cannabis in the house and it was totally trashed! They are members of the TPO s I am hoping they award me compensation to pay for all the legal fees and damage done to my property. fingers crossed....