No – you can buy extracted CBD compounds, but the flowers are illegal to buy or to sell. The same applies to CBD buds.
Hemp flowers are very high in CBD – usually around 13% to 15% and low in THC, generally less than the 0.2% benchmark. However, while such flowers are legal elsewhere, they are not in the UK.
Growers of cannabis or hemp plants require a special license, and even though hemp flowers fall below the legal THC limit, they are banned simply because they are part of a cannabis plant.