Appointments & Fees: scope creep, standard of care, and consultant coordination

You are appointed under a RIBA Standard Professional Services Contract 2020 on a £4.5 million private residential scheme comprising 22 dwellings for a regional developer client. The appointment was concluded at the end of Stage 1, the Services Schedule lists the Stage 2 to Stage 6 design and contract administration services, and the fee is a fixed lump sum of £315,000 plus a small disbursements allowance. At Stage 4 the client emails to ask you to take on three additional items at no additional fee. First, they want you to lead the discharge of fourteen pre-commencement planning conditions, including a contaminated land condition that will require coordination with a specialist consultant the client has not yet appointed. Second, they want you to attend the site twice a week during construction to provide what they call "active site supervision", well beyond the periodic inspection visits listed in Schedule 1 of your PSC. Third, they want you to "take responsibility" for the structural engineer's design coordination because, in their view, the SE has been slow to respond to RFIs and has issued two sets of incompatible information to the contractor. In a follow-up call the client also tells you they have purchased a "tested" facade design from another developer's recently completed scheme and they want you to specify it as the external wall solution. The detail is at the boundary of compliance with Approved Document B Volume 2 (the building has one block at 19m to top occupied storey) and you have not seen any test evidence. You re-read your appointment and notice the standard of care wording in the Services Schedule appears to conflict with clause 3.1 of the PSC printed form. The client signs off the email with the line "please confirm by Friday so we can move on".