hochimin67:I think they are just trying it on.
Perhaps they are but maybe they think the same of customers who accept estimated bills.
Whatever, you are entitled to be properly and fairly treated. TT Lady is right, £200 a month (allegedly actual) does seem high. I would slightly disgree with her use of the phrase "your responsibility" though customers at least share some responsibility.
Google for something called "The Code of Practice for accurate billing". BG are signatories. Go through it with a fine tooth comb and ensure that BG have discharged all their responsibilites. For example, they are required to estimate based either on previous actual consumption or on average consumption for your type of property. No way is £38/month average, so something doesn't stack up here.
In the case that the only omission on your part is not to have challenged estimated bills then I would say you are in a strong position to expect reasonable terms for the actual consumption. The Code of Practice customer perogative is only that it is "a good idea" to compare the estimate with actual.
In the first instance you need to verify that the BG Jan reading seems reasonable and obtain evidence of the previous actual reading. Then you need to check that the BG calculation is accurate for the type of meter you have. Details on your bill.