Cheers for all the replies everyone, and sorry for the slow response. You've been very helpful with lots of questions and I've had to get a chance to measure and whatnot. Heh.
I have been round my granddads and measured the tyres, and then realised the tyres have the size written on. Either way, they're 26 inch by 1 and 3/8 inch thick. That link is a good one so cheers for that, it is one of the pages I had looked at before though and only seems to have 3 speeds (this is a 4 speed judging by this: DSC00704.jpg
). Also, the tyre size is different, but the bike does look extremely similar other than that. The frame and fittings look practically identical in fact, so I may still delve further into that site.
Cheers for confirming the hub date is it 2 number year, 1 number month like I'd assumed? I still can't find any serial number on the bike frame but the site about the gear switch was pretty useful - as far as I can tell the bike has the GC4B (the one I have is pictured above) which indicated 1956 onwards matching the 1958 hub. Somewhat interestingly I think the hub and switch have different logos. Either the company was using both at the time or one has been replaced, so I need to look into that too. xD
$300 is a little higher than what I'd guessed (and it really was a clueless guess) so I wouldn't call it a bad price. I never mentioned this and probably should have also, but I'm in England, not far from London. I'm not sure how this would change the local price though as until I got the bike I knew nothing about bicycles...
That's a very nice estimate that he was happy to hear, I'd never had guessed it'd be that much. I didn't mention before though and should've - I'm in England, so not sure how that would change the going rate... I'm pretty sure I'd have to sell it locally as it weighs so much. Do you think it would sell just as well over here or no idea?
I passed on the compliment and my granddad was very chuffed. Haha. Cheers for that.
As best I can measure the bike frame is 23inch so it may match the one on this page, 17 down: http://www.cambridgeclassicbikes.co.uk/Bikes-weve-Sold (a green 4-speed, I know 17 down is a pain, sorry). I'm going to contact them and ask about the bike soon if I can't find any similar, nearer, company.
Phew, long post. Cheer again everyone for your replies, it's been quite enlightening already.