The GRO birth *index* does not show whether someone was subsequently adopted, but the actual birth certificate does (though not by whom, where or when - it just has the word "adopted" written on it).

You can order the birth certificate direct from the GRO (www.gro.gov.uk) using the reference information you have already found. If you want to avoid getting a "wrong" certificate, you need to check the "no" box when asked if you have the GRO reference (even though you do!). You will then get the chance to specify that you only want the certificate if the mother's name is Beryl. Ordering this way takes a little longer (about three weeks rather than one) but it costs the same (£9.25 including postage) and, although you have to pay up front, you will get a refund if there is no match.