Do you think its worth restoring? And what would you keep?
This was the bottom of the Holdsworth range. That's not to disparage it, but when you consider the potential costs in time and money of a full restoration, it looks more tempting to start with something a little more desirable. That said, I do understand the sentimental and personal reasons why it's this
bike you want to restore.
A full professional restoration on the frame, including transfers, could easily run well over a hundred quid. Have a look at the price list here:
The finish would be tricky to reproduce yourself. That said, it doesn't look to be in awful condition, and you might get away with treating the worst of the rust and giving it a waxing. There's something charming about the patina
of a frame that's lived a real working life. The advantage of cheaper, plain gauge tubing is that there's more metal there, so less risk of rust eating right through the tubes.
It's hard to tell the condition of the components from your pictures. Again, you have the choice between saving what can be saved and keeping it as original as possible, or replacing with better quality parts as available. A new set of wheels and tyres might be a good place to start, along with a new chain, cables, and bar tape. If the trasmission isn't in good shape, you could consider a conversion to singlespeed or a Sturmey hub. Older alloy bars and stems can be a liability. Check for corrosion and scoring.
There's always plenty of good, older kit on eBay, but it tends to be the case that only the collectable kit gets listed, and the rest goes to the tip. Cycle jumbles are a good source of older, quality parts that might not find a buyer (or two bidders) on eBay. You get to play with the parts hands-on too. There's a big one at Ripley in the summer:
I'd be careful about springing a surprise on your dad - he might like it the way it is! Parents can be funny like that.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.