I can see no reason at all why you can't exchange the surplus heat from the data centre and use it for the office space. 

I would expect your cost v. savings analysis to show a much shorter timescale than geothermal or solar heating for a house.

Instead of talking to air-con installers, have you tried talking to companies that install heat exchangers as their main business? I bet they'd know how to plumb you up.

Good luck.

I remain agnostic about whether it would be profitable or not, though it is perfectly plausible that a good scheme could be made to pay, but for a change I am moved to diverge from Georg's view. Pete seems nearer the mark. If it were an isolated situation of trying to match one's own consumption to one's own power supply from the heat pump or similar system, Georg might have a point, though even then one might argue that by turning down the heat pump when its output is unwanted, one might mitigate the least welcome importunities of an over-solicitous system. And then? Then some heat-energy might go to waste. But some would not and what did would have gone to waste anyway.

However, usually there will be more power sinks than sources. If there are network suppliers, then it might be that they could buy surpluses. (Apparently not applicable in this case, but...) If it is summertime, the aircon might want power,  and if winter-time, there is heating. I even have known a company that used its waste heat for a heated swimming pool.

The main objection to a viable system (apart from the ubiquitous NIH!) as I see it, is that the system is likely to be small and not off-the-shelf. Small is beautiful, but it often is inefficient too. So you get a small, dedicated crew putting together something that might work sort-of, but needs that crew for support. It might pay if one neglect's the dedication of the crew, or it never might pay. If the system were all off-the-shelf with instruction books and standard components, it might cost a tenth as much, but there seldom is much point to asking the opinions of the guys behind the counters of the local hardware stores, or the counters behind the piles of beans in the company offices. Nor are they likely to care about functions that deliver important services when other systems are down...

Their job is to tell you how it won't work, not how to make it work.

I may have quoted this before; I shall do so again from time to time:

Experts get their expert fun

Ex cathedra telling one

Just how nothing can be done.

     Piet Hein