I personally love stamps produced by engraving methods. I suppose that the
only way to collect QE LE stamps is acquiring them in auctions or
stamp-shops as they must be very valuable. Correct me if I'm thinking wrong
that stamp collectors do not usually exchange that type of stamps.

The basic 'Penny Red' imperf [1844 type cancel] can be bought on eBay
for about US$2-5 unplated. Often there are lots of 10 or more for
US$12-20. Those with the Maltese Cross Cancel do go a bit higher.

With these imperfs, margins are all important. If the design is 'cut
into' or even touched, the value drops. Typical VF margins are 1/16"
around.

The later perforated 'stars' are less pricy - and can be bought in
groups for UD$5-10.

Enter [ penny 1d red ] into eBay's search, selecting "Stamps"
category.

The last grouping ot the Penny Red [letters in four corners] are even
more available and les expensive. You can find the plate number in the
side 'spandrel' or border.

I suppose traders might exchange, though with the these, the postage
would outweigh the stamp value if done in singles.