What is the equivalent to Lyscordet?

Hi everyone

Couldn't find a newsgroup specifically for knitting or crochet but this one looks fun!

I'm based in the UK and am thinking about making a top using a pattern
that states you need 5 x 50g balls Twilleys Lyscordet. That seems to
be an expensive option. Just wondering what Lyscordet is comparable to
in the UK.... is it similar to double knit, 4 ply or something finer
than that.

Also wondering what size 3 fine (sport) weight cotton thread would be
similar to, in UK wool. I'm thinking of crocheting some bags for my
daughters. Would a 4 ply work instead of sport weight cotton, or would
it come out too big?

Please can someone help on either of the above two questions.

Many Thanks.

Yvonne