  We have obtained deep SZ observations towards 15 of the apparently hottest
XMM Cluster Survey (XCS) clusters that can be observed with the Arcminute
Microkelvin Imager (AMI). We use a Bayesian analysis to quantify the
significance of our SZ detections. We detect the SZ effect at high significance
towards three of the clusters and at lower significance for a further two
clusters. Towards the remaining ten clusters, no clear SZ signal was measured.
We derive cluster parameters using the XCS mass estimates as a prior in our
Bayesian analysis. For all AMI-detected clusters, we calculate large-scale mass
and temperature estimates while for all undetected clusters we determine upper
limits on these parameters. We find that the large- scale mean temperatures
derived from our AMI SZ measurements (and the upper limits from null
detections) are substantially lower than the XCS-based core-temperature
estimates. For clusters detected in the SZ, the mean temperature is, on
average, a factor of 1.4 lower than temperatures from the XCS. For clusters
undetected in SZ, the average 68% upper limit on the mean temperature is a
factor of 1.9 below the XCS temperature.
