Practice are now switching on access to patient records over the next few months, they have to do this by law, it sounds as though yours has already switched it on. There are issues to be worked through, for example if details of third parties are recorded in your record.
As far as who can see your record, anyone with access to the clinical system could see it, but it would be a sackable offence unless it was needed as part of your care. For example if you ask if a prescription has been done, the receptionist would go into your last entry on your record to check that out.
I think there is a possibility, at least there used to be, of 'sealing' your record so that only your GP and you can view it. This was used for GP's families registered at the surgery, who obviously didn't want any staff accessing their record. But to get that done you should make an appointment with the practice manager.
Most GP surgeries are now sharing their data with ICNs (integrated care networks, which took over from PCTs) The data is collected into one big database which is used by GPs for out of hours care, but also for admin and accounting purposes by the admin staff.
If you have concerns and don't want your data shared into the wider network, then it depends on which clinical system your practice is using. I am not going to cut and paste a large amount of data, but if you are interested, this document would help?
www.bma.org.uk/media/1366/bma-principles-for-sharing-and-accessing-local-shared-electronic-patient-records-2.pdf
I think if you do not want your counselling records shared, then tell your counsellor to keep them private, and not send to your surgery. You could also ask for a copy of anything s/he proposes to send in summary as a check. The hospice counsellors I now work with always ask for permission to share data with the GP, and will respect refusals.
The vast majority of NHS staff are acutely aware of the need for information governance, they have to receive regular training, and are aware of the consequences of unauthorised access.
Having said that, the human brain is a very curious creature, and when Richard Hammond from Top Gear had his terrible car crash in Yorkshire, a survey of access to his hospital records revealed 400 members of hospital staff had had a look, including from the Obs and Gynae department! They were disciplined...