keep in mind that with a sole proprietorship, you are able to claim the portion of the rent/utilities that you USE for conducting business. so, for example, if you use 1 bedroom of a 2 bedroom flat for your office, i think that you could reasonably claim 1/2 of your rent (if you want to play it safe, then 1/3). same for utilities.
when we moved house last time, we did it specifically for more space to carry out our business. so what i've done is claim the extra rent that we now pay compared to what we were paying before. i did this because there is no way that we would be paying what we are or living where we are if we didn't have the business. this extra amounts to over $10k/month, so is definitely worth it. also, because the place is bigger, we claim more for utilities, especially electric (that air con in summer kills us because it's on 24/7!)
if you do stuff by fax, then you can claim the cost of the fax machine plus the running of the fax line. same with internet. if you have a website up and running and you do a fair amount of business through email etc, claim your internet costs.
if you need to buy furniture for your "office", claim it as a deduction as well.