Non‑compliant loft conversion, seller angry at last‑minute price reduction request. What now?

In June 2025 I offered £390k on a house listed at £395k. Offer accepted. I instructed the solicitors the same week.

From June to August there was zero communication between my solicitors and the seller’s solicitors. I was following up regularly and kept being told my file was “progressing”, it wasn’t. I didn’t realise at the time how unacceptable this was. The sellers had already evicted their tenants at the start of August.

I eventually had to make a formal complaint to Barrett’s, and they escalated me to a senior solicitor.

In July, I hired a surveyor. They flagged that the loft conversion, which connects to the second bedroom, had no building regulations approval. Important context: this second bedroom was already a bedroom before the loft conversion; the loft was added to expand it. The surveyor said the work was shoddy and likely wouldn’t pass regs without fixes (fire doors, possible structural work). The outgoing tenant used the loft as the bedroom

I had raised the loft question with my conveyancers earlier, but not directly with the seller’s side

The seller’s agent says planning permission wasn’t needed (permitted development) and that they never marketed the loft as having building regs. However, the current tenant had been using the loft space as part of the bedroom, with a bed up there.

My concern: without building regs, I can’t legally market it as part of the bedroom in future, which could hurt resale value.

Today I asked for a £10k reduction to cover retroactive compliance and fixes. The seller’s agent is furious I didn’t raise this earlier, says I’m being unreasonable, and warns the seller may pull out if I push it. I’ve offered to offset this by deducting a month’s rent from the reduction as goodwill.

I accept I should have been more proactive, but I’m a first‑time buyer and didn’t know how this worked.

Do I stand my ground, compromise, or walk away?