Depends what you want it for.
For me I used to have one 30 yrs ago when i was a kid and wanted another one. It only will come out on dry days, but I love it.
The Bianchi is a dream bike, but for a Retro bike you can't beat a Raleigh. I love the black and gold scheme to it. It has a great looking 501 frame, however I believe the sprint you are looking at has the 531 tubes, which are better.
For £100 I would need it to be very good condition. There are several checks you can do. With mine again, I needed the GOLD anodised brakes,levers and front crankset. I had to add the Gold brake cables myself. The original wheels on mine were Black, and that is also what i would look out for if you can.
You can still get the original tyres off ebay, which I have but I am running a Mich set that have a yellow banding, again to keep it looking like the original.
If you are going down the lines of a rebuild, then the decals that you have on it are very very rare, I couldn't find any, because my next project will also be a Sprint version. So might have to take photos of them and get them made up.
Also very hard to get the original cassette as it is an 6 speed road version.
And also the cassette, chain and cranset where all Gold as well, although there are 2 versions of the crankset, I have the later version.
There are a couple of catalogue pixs that I have of the different versions of bike, they do look different, can post the pixs up.
Si