I would run three cases without inventing market growth: completed sale with minimal adjustments, a case including documented condition and charge differences, and a cautious case for unresolved area or rights issues. The spread will show which missing information is worth pursuing.
Finally, try once more to obtain completed comparables through the agent or another locally appropriate channel. Asking prices only show seller expectations. If completed evidence remains thin, that uncertainty supports being disciplined, but it does not prove the studio is overpriced. On the...
Before sending it, rank your variables: maximum price, completion flexibility, deposit amount and conditions, inspection rights, and what happens after a low valuation. You can trade flexibility on completion without trading away protections. If the seller counters, ask what would make the offer...