I've always thought that Guildford has narrow platforms, considering that the station sees very heavy commuter traffic (which it had even in my father's day).
Re Bicester North, it's good that the Up platform has just been widened with the existing structures retained, so that the original layout of through roads with platform loops can be reinstated if ever needed in the future. When BR singled the line between Princes Risborough and Aynho Junction, the 'dog legs' where the platform loops originally turned out were retained, the double track becoming single beyond these. I can remember this layout when I first travelled the line in the mid-1980s. Some years later, by which time I was living in Kidderminster, I can recall a DMU railtour from those parts which visited Marylebone. I was in the front coach and could see "over the driver's shoulder", and as we came careering down from Ardley with the speedo needle on the end stop (as DMUs did back then) I observed that the track layout at Bicester had been realigned, now with a straight, bidirectional route through the Down platform. A friend was sitting in the middle of the train, he was familiar with the line and approaching Bicester he was A Bit Worried, to put it mildly!