for complicated/amended OTP terms, always seek legal help.
it is only fair that both buyer & seller are legally represented, and terms are negotiated before exchanging booking fee for the OTP.
just like to share my experience in a recent property purchase with TA (negotiation of terms in OTP took 1 week):
1) seller's agent provided draft copy of OTP
2) I forwarded it to my lawyer with specific request to delete/amend clauses
3) amended draft OTP returned to seller via agent for their consideration
4) seller agree to terms by counter-signing at each amendment when they exchange the signed OTP (with copy of TA & duplicated stamp duty evidence for TA & inventory list) for my booking fee.
negotiation related to TA are via email between myself, seller agent & seller:
1) specific furniture seller wants to be return
2) state time frame upon expiry of tenancy for seller to move items in (1)
lawyers' work:
1) write to inform seller mode for return security deposit (usually via deduction of sales proceeds at completion; however bearing in mind that buyer needs to pay pro-rata maintainence fees) & access cards & keys etc etc; therefore statement of cashflow is usually prepared and agreed by lawyers of both side nearing completion
2) write to inform tenants new owners & monthly rental payment arrangement
3) follow up with tenancy stemp fee and other tax arrangemnts