Ok.
First off, regarding which was made where, I am not trying to suggest that one Whitworth Express Rifle is better than the other.
The reason for posting is merely to try and provide a very easy way to determine whether a Whit was put together in Britain or not.

If a Whitworth Express Rifle has the following.......

1...Whitworth banner on top of front receiver
2...Second recoil lug attached to barrel
3...Front and rear sights attached with screws
4...Serial No in the 200,000 up range
5...Rear bridge date stamp RH side in the 80's ie xx8x
6...V with a what looks like a crown above it on RH side of action and barrel

..........there is a good chance that it was NOT assembled in England!

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If on the other hand a Whitworth Express Rifle has....

1...Nothing on top of front receiver
2...No second recoil lug
3...Front and rear sights attached by SOLDERING
4...Serial No in the 100,000 range
5...Rear bridge date stamp RH side in the 70's ie xx7x

There is a good chance that it WAS assembled in England!

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So how do you tell for sure?
Easy, a Whitworth Express rifle put together in pommieland will have to have been proofed there and will be stamped accordingly.
It is often said that the so called Crown over V stamp shown on some of these rifles is an English proof mark and that this shows the rifle to have been put tgether in Britain.
This is NOT correct.
That Crown over V, if that's what it actually is, does not in any way prove that a rifle has undergone proofing in Britain.
Also that "CROWN" on many Whitworth rifles is so poorly stamped that it often appears more like a 5 pointed star than a crown making it a possible star over V.
Crown or star, it doesn't matter, that type of stamp is NOWHERE near what the true British proof stampings should look like on a rifle put together there.

Here is what the proof stampings should look like, or be very similar to, according to the British Proof Laws at that time.

First, the stamp of the proof house involved will be shown ,and to date all Pommie built Whitworth Express Rifle stampings I've seen were done at Birmingham.

Second, the cartridge chambering will be identified along with a pressure rating in Tons per square inch.

Therefore a Manchester Whitworth Express in, for example .458 Win Mag will show.

CROWN over BNP on both barrel and action
and
.458" 2.50"
19.5 TONS PER Square inch.
Note that the word "square" is not written but instead represented by a four sided "box", and 'inch' is shown as ".
Note 2 The cartridge and pressure stampings on many Whitworth Express rifles are located on the underside of the barrel and require the removal of the stock to be seen.

So there are the basics on identifying a Whitworth that has had some sort of assembly in Britain.

A Whitworth Express Rifle which does not show the complete set of proof stampings as listed above has NOT BEEN PROOFED in England and therefore cannot have been put together there.

Most Whitworth Expresses I have seen offered for sale on the net are NOT Manchester rifles.

I could write many pages on these rifles and their differences, but this will do for a starter anyway.