There are 3 good reasons every FTB should not be shy about making low offers in this twitchy market:
1/ It might be accepted.
2/ You're an FTB, so by definition, not under the same pressure to buy as somebody with an offer on their place accepted - if your first offer is accepted, you could probably have bought it for less. You have time to walk away from a few. Prices are no longer keeping up with inflation and are falling in some places. You don't need to rush.
3/ If every first time buyer low-balls sellers, then it will lower their expectations. Many other buyers already are. If you offer 400k and the two viewers both offer 410k, they are much more likely to counter-offer and negotiate with one. So, make a couple of low offers, eventually you'll make one to a fed up seller ready to talk - refer to point 1.
For people saying £50k is a lot of money... depends who to!
If you're a seller with a vacant property you own outright in London that's up for £450k, but objectively worth £425k, then the first £25k is in your imagination anyway. If you hang on for that £425k and it doesn't materialise, a 6% drop in prices wipes it all out - then you'll still have an unsold property in a declining market worth under £400k.
On the other hand, if you're a first time buyer, at the current standard variable rates, borrowing another £50k to rush in with an asking price offer because "it's perfect" will cost you about £275 a month for the next 25 years.
Food for thought?