Defence - Breach of Contract claim - small claims court - London, south East UK

Defence breach of contract claim. for £9,500. I viewed a beauty salon business (lease hold £20,000 a year rent) in Sussex and upon viewing accounts my accountant advised me it worth approx. £39,000 - £40,000 based on its Net Profit of just under £20,000. I offered £40,000 to seller (claimant) which she happily agreed but later became greedy and started asking for £45,000. We agreed and signed a contract for £45,000 purchase price + stock price which was valued on the day of completion for £18,500 on 10.6.16. Agreement was £20,000 be paid upfront and remaining balance of £25,000 + stock price of £18,500 be paid in monthly installments. C offered to work temporarily part time for free to keep an eye on the business but being kind I insisted she be paid. C agreed to work on £11 an hour at the salon. Claimant lived just 5 min walk from this High Street salon and I lived in London so I rarely went to salon. But within 3 months it was obvious C was manipulative and over ruled me and under mined me at every step. Staff were loyal to her since she hired them. C acted as if it was her business and always over ruled me. C even made threats to me last September (while I was attending a funeral outside London in my family)that wages be paid 2 days before due date (due date being weekend) otherwise, she would tell staff to do a walk out and close down shop. Upset and stressed I put the business up for sale last September. Agents asked for last 3 years accounts of the business which were in C's name and valued the business at £40,000 and told me Net Profit of £20,000 was wiped out after C drew her wages of almost £24,500 and her business made a loss of some £5,300. I bought a loss making business. When I confronted C she resigned and said I was provided with accounts and it was mine and my accountant's responsibility to check accounts. The way accounts were prepared it showed Net Profit on one page and C's wages on the next page. So we didn't spot it. Agents put business on various sites on Google and I have now sold the business for £40,000. Agents told business was not capable of achieving more than 40k. Now C has filed a county court claim against me for remaining £5,000 of £45,000 contract price + remaining balance of £4,300 stock price (which I have offered to pay claimant) but C didn't reply. I am not prepared to pay c more than the valuation price. I rang a Sussex firm of solicitors who said they would take up my case and say £45,000 was over valuation and I have paid correct valuation price of C. I have honoured £4,000 worth of Gift vouchers C sold for massages, facials, pedicures for which C didn't remiburse me. There was nothing in the contract to say C would reimburse me for Gift Vouchers so I don't know if I can bring a counter claim against for it. (2) I might have a claim against C for Return of wages I paid Claimant for work she didn't do but provoked my staff to rebel against me and issue threats to me. (3) defamation claim against Claimant that she slandered me before my staff and clients by going to my salon for free treatments and talking against me before both staff and clients. Due to that 3 staff members who C had hired walked out and I didn't have enough staff to do bookings. My turn over fell. At least 2 of new therapists I had hired this year reported Claimant to me begging me to stop her visits to the salon and she was damaging my business. Both Marie and Poonah who I had hired offered to give witness statements that C was having free treatments at the salon and talking against me. C also took free bottles of Guinot and Clarins from my salon. You will I was very kind to her but she back stabbed me. C even went to my salon to introduce my staff to a rival salon due to open in few months times in order to transfer them to the rival salon and told my staff to leave my employment and go and work for that salon. When it was reported to me by Marie I was furious and rang C but she denied it. When I asked a senior therapist Steph she admitted that meeting was arranged by C to introduce them to the owner of rival salon. I sent emails of complaints to sell's husband and their ex solicitors. Can you take up my case please.