You'll find that all auctioneers will take additional bids, besides the ones on the day, in the form of "prior bid" or "auctioneer" bid .. as well as phone bids when the actual item is being sold.
The idea with "prior" or "auctioneer" bids is that you leave a bid offer with the auctioneer, before the sale starts.
Say you offer $300 for the radiator. The auctioneer will note it as a firm and genuine bid, and he will commence the bidding at that figure, by saying something like .. "Here we have Item 1557 - a restored British Bedford radiator. I have a bid of $300. Any advance on $300?"..
At this point, bidders in the crowd will be a little stunned and considering whether to bid it up more. Sometimes there will be no more bids .. and the item will be knocked down to the the prior bidder .. and sometimes there will be bidders in the crowd, who reckon it's worth a lot more .. and the bidding will start at $300, and go up from there.
Prior bids are generally low, and for items where the bidder thinks there will be low demand .. or he might just put in a modest bid, hoping to score it.
Regarding phone bids, the problem is trying to determine when the item is actually being put up for bid. Most auctioneers know reasonably accurately, how many items an hour they can get through .. but sometimes, they can fall well behind, too.
Thus, you could be calling them a dozen times, trying to get an idea as to when the item is actually being put up. Usually phone bids will only be taken on sizeable items where the bidder numbers might be low, and the auctioneer is looking for extra bidders.