Hurr1cane - different centres / doctors deal with situations like you are in, in different ways, but generally:
If your blood levels have doubled or more, so in your case is 492 or more, then they will probably assume it is an early pregnancy and just recheck in a few more days with a scan / bloods.
If your blood levels are more than 60% but not quite doubled, so in your case between 393 and 492, then they will start talking about a possible viable pregnancy but also possible miscarriage or ectopic still and will definitely want to repeat bloods in two days and probably scan. You will have no answer on the day.
If your blood levels have increased but not at 60%, so in your case increase to somewhere between 246 and 393, then they will be thinking that it is probably a non-viable pregnancy, either probable miscarriage or ectopic, they may again monitor bloods again in two days, and repeat blood tests until it reaches 1000, or starts falling or if you get other signs that increase odds of ectopic. Ectopics are rarer than miscarriages, but the risks of missing an ectopic are high, so they will act cautiously with you.
If your levels have fallen below 246, then they will often treat you as if you are miscarrying.
With your bleed two weeks ago, if it was an implantation bleed, then your levels have already risen very slowly, so it would surprise me if you get a clear doubling tomorrow. Doctors like taking numbers and treating them as if they are a definte answer. Slow growing hcg does not mean inevitable bad news but doctors almost always act as if it is. It is right that they should act with caution in your situation, pregnancy of unknown location is difficult.
If you get "prune juice" bleeding, shoulder tip pain or definite sharp one sided abdominal pain or fever then return to a&e immediately.
I hope you get your answer soon, it is hard for you not knowing.