[londongardener]

Do they really need to be planted 5 ft apart that seems a lot?
Also can anyone suggest a type of raspberry which is good and fruits after the end of August?

[mumofstig]

Joan J is a very reliable autumn fruiting raspberry, harvest August, September and the beginning of October.
Just finished here 

[Nobbie]

Do they really need to be planted 5 ft apart that seems a lot?
Also can anyone suggest a type of raspberry which is good and fruits after the end of August?

Yes, if your soil is good and they're a reasonably vigorous variety such as invicta or leveller and you're going to leave them to grow as a bush, then you'll need that space to get around them for picking and pruning.

[greenjay]

second joan j fab raspberry

[Dev]

And I would second Nobbie. I planted a number of bushes too close together and gathering the crop is a real proverbial pain - literally, as my hands tend to come out looking like I've been playing with a lively kitten! The middle ones are going to be moved this autumn.

[londongardener]

I have just realized that presumably it also needs to be 5 foot from the edge of the allotment plot?  Or is that not so important?

[andreadon]

I have just realized that presumably it also needs to be 5 foot from the edge of the allotment plot?  Or is that not so important?

No. The growing distance is normally to allow for growth. So if you can get to it and it doesn't encroach on the path then it doesn't have to be that far from the edge. I'd probably go 2ft 6" from the middle of the plant