'Many agents have reverted to sealed bids only, with properties fetching £30-40k more than the asking / guide price.'
Sounds about right. There has been much silliness in the property market of late. I was outbid on a property recently, only for it fall back in my lap about six weeks later. The original 'buyer' couldn't obtain a sufficient mortgage. After they attempted to beat the vendor down £15k, it was offered back to me. I agreed to buy, but at less than my final offer, and am now waiting to complete.