As Ethel says, most NHS authorities give out digital hearing aids these days.... none of which *whistle*.... You may find everything a bit *loud* at first when wearing your new hearing aid, but you will soon get used to the (normal) sound !
You may also find it helpful to hold your office phone in a slightly higher position when answering the phone, as the hearing aid is positioned behind your ear, the phone receiver needs to be picking up the sound at that point, not in the middle of your ear.
Expect a wait of a few weeks whilst your mould is made btw and ask them to show you how to change the tubes - the secret is to cut the tubes on a diagonal and slide them through the hole, or just post another Q here...
Good luck Louise !