I also find a Wellbrook loop works well and in fact it's been my only receive antenna on 630 m until quite recently. As Tisha says, it's worth doing dome optimization of the installation and some careful checks on completion: if you're not getting good deep LF/MF nulls, keep going. Mine is in as good a location as I could find on the suburban block, mounted about a loop diameter above a garden bed. The RG8X coax is largely underground and, interestingly, I didn't notice any significant improvements as I tried various extra choking and decoupling tricks. However, that's no doubt a function of the particular installation.
Recently I tried a homebrew 10-turn, tuned, frame loop, with a single turn coupling loop on 630 m. It's not broadband (well, not without adjustment) like the Wellbrook loop but I've found it's pretty much the equal of the commercial loop around 475 kHz. I'll probably keep the Wellbrook loop for my main station, and use the 1 m square frame loop for the separated MF station. That station is built around a rack mounted TS-590S and a homebrew PA; the frame loop can be split between the TS-590S receiver and an SDR as required.
73, Peter.