The house itself was clean and comfortable and a pleasure to stay in, having everything we needed. The views are incredible as it is halfway up a mountain - definitely worth bringing a car unless you are a super-keen cyclist. If you do bring a car then I recommend not getting a large one - the rental company at the airport offered us an upgrade to a Nissan X-Trail 4x4 for only 10 euros in total (from the Qashqai we had originally ordered) which seemed like a bargain until we got to the extremely narrow streets and tight corners of Soller's old town (which you need to pass through to get to and from the property). Those streets were probably designed for horses riding single-file rather than cars! It was do-able but very tricky (particularly if you are not used to driving a large car) and a bit stressful at times.
That aside, I would still highly recommend staying at this house. Miguel and Eva were very helpful and personally guided us to and from the property on our arrival and eventual goodbye - this was especially helpful when we were leaving as it was a festival day and many of the normal routes to get out of Soller were closed.
One other recommendation is to follow the signs in the town (i.e. to Palma, Fornalutx, Port de Soller, etc.) rather than a Sat Nav - our TomTom insisted on trying to take us through the tiniest streets and ignored the one-way system in the town, sending us in circles over and over. The one-way issue seemed to apply throughout Mallorca. Follow the actual street signs and you will have far more success!
Thank you Miguel and Eva for your swift replies, flexibility and help - we had a great time here and would love to come back again :)