TinyUmbrella won't be able to do it by itself and there is no magic to download SHSH blobs if Apple is not signing them.
BUT, the good news is that Cydia does save SHSH Blobs every time you open it... so most likely the answer is YES, your SHSH blobs are saved (open up Cydia and check the top or bottom -don't remember- and it should list the blobs it has automatically saved for you).
So if Cydia has the blobs then you can use TinyUmbrella with Cydia option to try and restore with that old firmware version (I never did it before, I always locally save the blobs with TU, so I'm not sure how perfect Cydia signing server works).
By the way, so you don't confuse things, the SHSH blob is basically like a digital handshake file that is issued by Apple (or created locally, either way is has the ID of the device and other things) and when restoring via iTunes it uses that key to communicate with Apple servers and then if the key is correct you can use that firmware version.
What TinyUmbrella does is, it uses that key saved locally or via Cydia and creates a fake signing server so when iTunes calls home, it's in fact calling TinyUmbrella/Cydia and if the key is correct (saved locally or on Cydia servers) then it allows the firmware restoration.
Why they haven't cracked the server to work so that you don't even need a SHSH blob, beats me, probably a hard-as-hell encryption system is in place.
So this has nothing to do with a jailbroken device being able to just "grab" SHSH blobs for any firmware just like that (and I think SHSH blobs were made anyway by Apple to stop people from jail breaking).
I stand corrected.@ipsychedelic:
It works a bit differently as described
As 5.1.1 is still signed TU DOES do it by itself.
Thanks guys for ur replies , much appreciated. I'm kind of new to all this so don't really understand it all fully, is there anything I'm supposed to do now or is it all sorted?