New user from Scotland with a question!

Hi I'm Jonny from Bridge of Weir near Glasgow in Scotland. I'm on my 2nd Octavia vRS and I have loved them both! My current car is one of the limited edition models that were produced before the facelift model was released. I have the bolero radio head unit in the car and the phone button only mutes the audio. From reading other forum posts I understand this is due to it not being a factory fitted option. My question is, is there a kit available to upgrade the unit to be able to connect my phone to it? I have checked a few car audio web pages and I can get a phone enabled unit for £299 but obviously if I can convert my existing unit for cheaper I would rather do that. Any help would be greatly appreciated! Thanks in advance!!