The first 26 pins are the same between the old and new boards. So physically they should work. There are a few caveats to that however:
- most 26 pin headers will not clear the extra pins on the newer B+ and Pi2.
- The method used to enable I2C, spi and other kernel modules has changed.
- the software (drivers etc.) may not work with the newer OS images.
You can overcome the first by getting some stacking headers, and the second by doing a little research. The third may be a harder challenge to overcome. I would suggest you email the manufactures or check their websites for more detailed info.
It seems someone over at Newark has already asked this question for the PiFace
Yes, PIFACE DIGITAL 2 is compatible with Raspberry Pi model B+.
Things don't look as promising for the MEMS Sensor Kit. According to Element14 while the hardware does not seem to be a problem, it appears the software (driver poses some problems). Though the posts that mention a problem are from September 2014. This page (last comment) hints that there maybe some hope