To give you an idea on value, from my experiance only. I bought my viking goldstar for about £35. It was advertised at £50. It was rideable straight away.
I have bought it new tires, wheel tape and innertubes for a about £20. £15 for old front derailleur. £6 for new break pads. £65 for brooks saddle and brooks tape. I have also spent about 10-15 hours polishing all the bits up, especially the wheels, attacking them with cola, tinfoil and tcut. The chain was covered with delightfully thick engine oil, which was a good thing as the chain has survived nicely.
I am not going to send it off to get it resprayed. I only bought things for it that could be easily taken off and put on a better frame if it comes along. I dont think its worth getting new wheels or brifters as going down that path may require widening the rear spacing. If you are in to fixed gear conversion i suppose you could have a practice on the goldstar.
I would hope that mine could be worth £150.. it is unlikely to be worth more as the frame is not marked as anything special (no reynolds stickers) and it is not the lightest. I am just enjoying riding a bike from ~1976 (the date is on the breaks and crank)