When I had Aquiss install my line, the fee was £60, but there was a line contract of 12 or 18 months; this works out far cheaper than what BT charge (£150-£180 install and £20 per month v £13 per month with Aquiss).
There was no requirement to take an internet or telephone service with them though.
I would leave it up to whoever wants to rent the property, put it in the contract that you will pay for the install with whoever they want to sign up for; that way you only have to pay the install fee, and not any rental fees, or cancellation fees.
I am currently refurb'ing a rental for my sister; the tenants burnt candles in every room for the whole time they have been in there; every wall and ceiling has a liberal coating of smoke and tar embedded into the paintwork - which they hastily over-painted before moving out - so of course, their paint is now falling off the wall if you so much as touch it.
I had a 2 week turnaround planned, yet 3 weeks in and I havent finished the first two rooms yet.