Set your maximum bid, and wait and see. EBay will bid automatically for you, up to that amount. And earliest bid wins if they’re the same.
Sometimes the snipers win, sometimes they don’t, but if you don’t win, it went for more than your maximum, so that’s ok.
But don’t bid a round figure. If your maximum is £20, then bid, say, £20.06 to beat someone else’s £20.
Prices realised in e-Bay auctions can be very unpredictable. I’ve seen vintage items sell for far more than ‘the going rate’. I have also picked up a few rare and interesting pieces which were mis-described and very cheap because there were hardly any or no other bids.
It does make a difference where something is being sold. I sometimes used to attend a local auction which included toys and models, from time to time even the entirety of the equipment from a dismantled layout. I also occasionally went to the specialist vintage train auctions held in Rugby. It was possible to get rare items cheaply in the local sale as other bidders generally did not realise the model’s significance, nor did the cataloguer. Not so at Rugby with a room full of experts and dealers. Conversely, a nice Bassett-Lowke lithographed Royal Scot, for example, would sell at a top price (or more) in the local sale. It would go for far less at Rugby because, as a fairly common model, all the attendees already had one.