Real Tilde Symbol on Macbook13 is missing Can only find the superscript one

No I haven't tried that for the simple reason that there ain't no # key on the Macbook 13, it only has # by using alt+3

What puzzles me most is that the ascii character set seems to be limited on the Mac but you can bring up any character you like to name on a Windows computer.
Excuse my using dirty words like that on a Mac Forum! Surely even a typewriter has a hash key. Even the tiny keyboard on my Blackberry has a # key on a shift-Q
So who goofed with the Mac?

Yes I have just done that operation and only one item British (PC 105 Alt) is the only one ticked.

I don't think it's worth going to fetch any other British Layout because all the answers here so far have not shown that there is a genuine Tilde on the mac keyboard. The language won't make any difference as the Mac system seems to me only to have put a Superscript tilde on the machine. Superscript isn't a proper Tilde, it's one merely for placing over the top of a letter and that's not the one that I used when making a Password for entering a shopping site when I registered using my Windows PC.

So unless anyone here knows that there is a real Tilde sign lurking somewhere then I'm sorry to say the question still remains open.

Thanks anyway for your input, I'm grateful to so many people trying.
I've not given up yet but nearly have!

I'm about to mark your very useful suggestion as having solved the problem - not because you found it but because you inspired me to try some random Shift+ lots of different keys until I found one that worked.

Yes the Tilde is there and the key it is on is just left of and next to the Enter Key which has printed on it a back-slash but that isn't what comes out when I press it. Pressing the backslash key gives me # (yes a hash sign) The shifted symbol written on the key is a single vertical line (I don't know what you'd call that) but Shift + that key gives a genuine Tilde thus: ~
But I noticed also that Alt+ that key gives « (two "less-than"chevrons)
Is this a googley of a keyboard or what? The only thing I ever did to change the keyboard layout was to swap the " and the @ to opposite keys as the Macbook placing of an @ sign on shifted 2 was very peculiar and not seen on any other keyboard by me.

Anyhow I now seem to have my Tilde but I've lost my Back-slash symbol.
So how should I mark the question if it has been solved but produced another problem in exchange for it? This is getting silly.

I didn't get the British Layout anywhere - it was on my Macbook 13 purchased new in the UK.
I've been to the Layouts and note that there is a British Layout with a ghosted tick in the box that can't be removed. There's two other British Layouts one showing in Brackets (PC 105) and the next one down is British (PC 105 Alt) it will allow me to tick either of those two latter ones but when I untick them the ghosted British one still won't allow me to Tick it. So I can't really do much about that.

Anyhow as you see from another of my replies here I've found the result but imagine my frustration having to put a document on my desktop to remind me that on this rather muddled schizophrenic keyboard I have to know that symbols marked on keys are nothing related to what they really do.
That document I have written the following:-

\ Backslash is on standard key left of the figure 1
# Hash is on backslash key next to Enter key (just to left) Hash is also available on Alt 3
~ Tilde is a Shifted key to the above Hash one.

I will need to refer to it next time I want to use a \ or a ~ or a # as I can't speak pigeon-macbook!

I will, if the page will allow mark your response as Helpful because you have done a very thorough analysis of my system. I still don't know how that PC105 alt got in there but in the back of my mind I think I may have been advised to fiddle with the configuration of the keyboard in the past couple of years when I wanted to swap the @ and the " onto the keys I normally expect to find them on most PCs

I do remember opening that keyboard list once before as I was told to select something else and that could be where I first had the flag and the British (PC 105 alt) appear on the top menu bar just to the left of the Battery % sign. But 2 years or more is a long time to go without ever having to go into the System Preferences and so it could be my mistake. If so I'm apologizing for misleading you.
The fact that you took me up on that does rather prove you do know what you're talking about.
I feel very confident asking questions here on this forum for that very reason.

If I untick those other two British Keyboard layouts, I'm fearful that it will revert to the old layout that kept tripping me up because of my years of getting used to "automatics" in typing on normal layouts. The Macbook has a whole different way of working that I've had to re-learn. There's no number pad. No dedicated F keys (they are all shared with other functions due to lack of space.

Anyhow I won't rabbit on here. I'm grateful to you for your help and I've solved this problem and now can at last find my tilde sign. Thanks muchly for your help and the others in this thread all of whom have helped in one way or another.
Cheers
--
Plado