Pros
Very good benefits - pension, guaranteed annual bonus, work from home 2 days a week
Work life balance - from AD and below work life balance is good. Most people leave by 6pm. If you get to SAD and above then it's the usual long agency hours.
People are generally nice - not too may agency d1ckheads.
Campus benefits - pretty much everything you need is on campus. Multiple restaurants with subsidised food, cinema, little Waitrose, quality 24 hour gym, free fruit, modern buildings, hairdresser, laundry service and great cycling facilities
Client relationship - as you are at the same campus as your clients, you will see them often and this generally fosters better relationships with them. Not an "us and them" mentality at some agencies.
Mental health - lots of initiatives to help with employees mental health
Cons
Senior management - Account Management seniors are pretty average. If you are looking for inspirational leaders then this is not the place for you. Senior management are quite dull and seem out of their depth. Team meetings are un-inspirational and seem like a box ticking exercise as there is no value to them. One example was when a senior asked everyone to stand up and then said "sit down if you want to do exceptional creative work". Just pointless... Numerous meetings about changing things for the better but nothing is ever done to change the root cause of inefficiency and dissatisfaction.
Job titles - your role will actually be a level lower than at proper advertising agencies (Account Director is equivalent to Account Manager). Most of the role is admin based - organising meetings with senior management and clients, running around getting approvals from multiple internal stakeholders.
Lack of creative input - at best you will be allowed to present the intro slides in a client meeting. You will create the document for others to input work but the selling of the work is done by the creative department. More of an admin role than a creative one. If you are a yes man then this is the place for you because any challenges/suggestions to seniors is treated as not being a team player.
Too many stakeholders - all work has to be reviewed and improved by multiple internal stakeholders. This is very time consuming and frustrating as you never get decision makers to agree with each other. This is very inefficient and leads to watered down creative work. Senior stakeholders are also hard to get hold of so things move way slower than they need to.
Frequent redundancies - every 12/18 months there will be a severe round of redundancies (between 10 and 20%) so job security is not strong
Location - commuting to Isleworth is a hassle, especially by tube. You have to get a shuttle bus to/from tube stations. These are frequently busy
No culture - as location is so far from London, everyone goes straight home after work. Nobody goes out socialising together and team nights out are sparsely attended - mainly because they are quite dull
Creativity - Sky are very risk averse and generally only want vanilla work. This is caused by multiple stakeholders unwilling to take any creative risks. Creativy is watered down during the creative process, with frequent changes of mind, changes to the original brief and JFDI's from the client. Senior management/creatives unwilling to stand up to the clients.