Fitting vents in a fascia/soffit board?

The front of my house has a fascia and soffit board arrangement. I am planning on using the circular soffit vents for this.
The problem is the back of the house. This has a fascia board but no soffit. How can I add ventilation to this? I would like to do this without taking the fascia board down.
I have seen a ventilation pack in Screwfix (Quote16198) http://tinyurl.com/jmwx . Could this be fitted to my type of installation?
The house is a semi so would the adjoining roof be a problem?
Any other suggestions please?
Regards,
Rich
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Over fascia vents - give a 25mm vent along the length. They are an inverted U sect than sits on the fascia top edge.
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