Hello philipturnbull,
Well on Vista the svchost.exe runs constantly and acts as a bridge between the system and un-automated DLL files which cannot run themselves, hence the need for that program,
However it could be down to something else that is run by svchost,
Try
1. Select 'Start' and type 'Event Viewer', press enter
2. Once loaded, On the left hand side select 'Windows Log' and then 'Applications' then 'System'
3. Check both of these reports for the sign of anything that occurred roughly when these issues began and they should point to the actual source
4. You can then select 'Actions' from the top menu and 'Save Event' when you feel you found a suspicious event
Let us know if you find anything,
Might be an idea to try and reboot in 'Selective Mode' and reactivate the services one by one to see if you can narrow down a faulty program
'Selective Mode'
1. Select 'Start' and type 'MSConfig', Then press enter
2. In the 'General' tab select 'Diagnostic Startup'
3. Select 'Apply' and 'Exit With Restart'

Regards
Craig
Well on Vista the svchost.exe runs constantly and acts as a bridge between the system and un-automated DLL files which cannot run themselves, hence the need for that program,
However it could be down to something else that is run by svchost,
Try
1. Select 'Start' and type 'Event Viewer', press enter
2. Once loaded, On the left hand side select 'Windows Log' and then 'Applications' then 'System'
3. Check both of these reports for the sign of anything that occurred roughly when these issues began and they should point to the actual source
4. You can then select 'Actions' from the top menu and 'Save Event' when you feel you found a suspicious event
Let us know if you find anything,
Might be an idea to try and reboot in 'Selective Mode' and reactivate the services one by one to see if you can narrow down a faulty program
'Selective Mode'
1. Select 'Start' and type 'MSConfig', Then press enter
2. In the 'General' tab select 'Diagnostic Startup'
3. Select 'Apply' and 'Exit With Restart'
Regards
Craig