We present the results from a submillimetre (submm) survey o f a sample of 23 giant Ly α emitting nebulae in the overdensity at z = 3.09 in the SA 22 field. These objects, which have become known as Ly α Blobs (LABs), have a diverse range of morphology and surface brightness, but the nature of their power-source remains un clear, with both cooling flows or starburst/AGN ionised winds being possibilities. Using th e SCUBA submm camera on the JCMT, we measure the 850 μm flux of a sample of LABs. We present detections of submm emission from four LABs at > 3.5σ individually, and obtain a modest statistical detection of the full sample at an average flux of 3.0 ± 0.9mJy. These detections indicate significant activity within the LAB haloes, with bolometric luminositi es in the ultraluminous regime (> 10 L⊙), equivalent to a star formation rate of ∼10 M⊙ yr. By comparisons to LABlike objects in other regions, we show that there is an appare nt tr nd (although weak) between observed Lyα emission and bolometric luminosity. Combined with our dete ction of ultraluminous activity in this population and the lack of any stro ng morphological correlations in our sample, this provides evidence that the interaction o f an ambient halo of gas with a galactic-scale “superwind” is most likely to be responsibl e for the extended Ly α emission in the majority of LABs. Assuming the extent of the LABs reflects outflows from a superwind, we estimate the age of starbursts in the submm LABs to be in the range 10–100Myr. Using the average submm flux of the LABs, we determine a star-format ion rate density in the SA 22 structure of>3M⊙ yr Mpc, greater than the field at this epoch. The submm detection of these four LABs means there are now 7 luminous submm galaxies in thez = 3.09 structure in SA 22, making this the largest known association of these i nt nsely active galaxies. This clustering further strengthens the proposed evolutionary link between these galaxies and local cluster ellipticals. Finally we suggest that the highly-ex tended Lyα haloes (which define the LAB class) may be a common feature of the submm galaxy populat ion in general, underlining their role as potentially important sources of metal enrich ment and heating of the intergalactic medium.