48817 units at even 10p a unit is £4,881.70.

I think your meter must be faulty. Most people have a 100 Amp suppy, so at 240 volts the most they could draw is 24 kw. 48817 divided by 60 days, divided by 24 hours gives 33 kw. If you had used this much the main fuse would have blown.

Ask the company to put another meter in parallel with yours for a few weeks to check it.