I have bedbug.where can I get boric acid powder(flea powder) in london?

i have to a new house and it has bedbugs. i am not sure if i have brought them in from my previous place because i had bed bugsthere as well. I can not afford to pay 100 pound to a company or someone to come and kill them. i heard about boric acid powder for carpets that might help a bit. if you have any other idea plz let me know. thanx