that's an interesting one!
the reasons its not generally a good idea to put a property into a company are
1. double hit to cgt - ie, to realise the investment firstly the company sells the property and pays 20% cgt. then the shareholder winds up the company and is distributed the after-tax proceeds. at that point another 20% cgt is payable because you are deemed to be selling your shares
2. if a property is held personally then you can "gear up" on it if it goes up in value (ie, borrow against the built-up equity). if the property is in a company then it is not possible for the individual shareholder to do this
3. the corporation tax rate on rental profit is 25%
4. if after-tax rental profit is not distributed out within 18 months then another 15% corporation tax is payable
however in your case it might be that there is no "rental profit" because the rental income would be matched by the mortgage interest. If that's the case then reasons 3. and 4. above go away.
your company would be audit exempt but you'd still have the administration costs of setting it up and then filing CRO returns every year + handling other company secretarial issues.
overall i don't think its that bad of an idea - you have to weigh the double hit to cgt (in the future) against the benefit (now) of the tax deduction for the interest. you'd need to run the figures with some assumptions and factor in ongoing costs of the company administration etc, to evaluate it properly. Eg, assume say 5% growth in value p.a. and a sale/unwinding in 10 years time, assume rental levels and mortgage interest costs over that period + admin costs of say 500e p.a. + unwinding costs of say 1000e. worth considering