The minimum time it takes for Natural England to look at an application for a licence is 3-4 months - 2 months for them to consider it, 1-2 months to get back in touch with you. They don't refuse applications, just ask for more information. If they ask for more information, it's another 3-4 month cycle at the end of which they won't refuse, just ask for more information...
You will almost certainly need a new bat survey to accompany your licence. Our previous survey was 18 months old, and we were on the border line of needing a new one.
The upside is that if you go ahead and get a new bat survey done, Natural England won't return your application asking for a new survey.
The downside is timing. You can only have a bat survey done when the bats are out and about ie between April/May and September/October.
Timing generally can be an issue. Consult the ecologist sooner rather than later in case you need a new survey/licence etc - we very nearly got caught out by this, and it was only because our building had suffered in last winter's storms and was becoming dangerous that we were able to get on with our building plans.
Your application comprises of several parts, one of which must be done by an ecologist (the method statement), one of which - the reasoned statement - can be done by you or a different consultant. Natural England publish lots of info on how to complete the reasoned statement, but do so in such convoluted jargon-filled language that you may feel you need to employ a consultant to translate. Worse, there are hardly any examples to be found via Google.
Ecologists vary in their attitude. We found some were a bit confrontational and antagonistic, others were more laid back. I spoke to one it wouldn't be too far a stretch to describe as fanatical (luckily, not working on our build). With hindsight, I'd have shopped around a bit to find the more laid back kind.
The bureaucrats have created a system that doesn't really work with the real world. It can lead to problems eg our scaffolder told me he was having to go to a NT property and take down the scaffolding each night so the bats could have unimpeded access to the roof, then return first thing to put the scaffolding up so the builders could get on with the work during the day. Our first mitigation statement was like asking us to make an omelette without breaking the eggs. We're currently working under the third mitigation statement for the property.
It's worth looking at Natural England's mitigation guidelines. http://www.naturalen...ecies/bats.aspx It definitely helped to know what the minimum and ideal requirements were, both for designing our build to accommodate the bats and for justifying what we were hoping to do to the ecologist.
It's expensive. The original report/survey/mitigation statement required by planning cost the owner c£2000, and we have paid another £2000 on top - although luckily, in the end we didn't have to have another survey or get a licence due to the building's condition. The licence would have cost c£3000 (including another survey) with me writing the reasoned statement.
The bureaucracy has meant that some people take extreme - and illegal - steps against bats, which is a pity. I heard of farmers taking the roof off barns before applying for permission (another chapel near us went for auction recently without a roof but Google earth shows it was in tact last year), hoovering lofts and beams to eliminate any signs of bat presence, putting up floodlights, even bringing in cats.
It's a real shame, as the bat population is under threat and they are losing habitat. And they are fascinating creatures! We've ended up with exactly the design we wanted, which also allows our bats their space, so having bats doesn't have to be a disaster.
One of ours (and before anyone can say it, it's being handled by a licenced ecologist, not me).