Thanks guys,
The owner said he has a fault code reader and that's how he found out it was turbo solenoid. By all accounts whilst fault is on the cruise control won't work? He clears code then for around a month all is back to normal. Forester is a 2.5xt on a 55 plate with 66,000 miles. has a few other issues, main one being no service history, mad I know.
I'm looking on Autotrader and ebay