Medieval people are well known to be smaller than us, right? Just look at all those small doorways in old houses. Well, here is a new study (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0275448) from Norway which suggests they weren't that very different to us. Certainly to me, who is around 5ft 9in or 175cm.
(https://journals.plos.org/plosone/article/figure/image?size=large&id=10.1371/journal.pone.0275448.t002)
Noticeably shorter than modern Norwegians, though, who tend to be a tall lot.
If the time curve in Norway is like that in Sweden, medieval people were relatively tall, their Early Modern descendants got progressively shorter - probably due to a dietary shift from meat and dairy to cereals - and then heights increase again from the 19C.
There is a summary of a paper comparing height in English populations over the last 2000 years. I haven't looked at the actual paper to see how the different classes compare, but the finding s are broadly similar.
There is variation over time but a lot more of a roller coaster than I thought - higher points in Roman times, the 12th century and the 16th century with lows particularly in the 14th and 18th/early 19th.
come to Wales, we are mostly short houses
I think Peter's point about variations over time and regions is well supported. The minimum height for a French conscript into the Revolutionary Army was 1.5 Metres (5 foot 1 inch) with evidence that was after a period in decline in the health and height of the general population, with a recovery in both occuring later in the 19th Century.