How we got there...
We flew in to Warsaw from 'London' Luton with EasyJet. We then had a short bus ride to Warsaw Central Station followed by another brief bus ride to West Warsaw Station. From here we caught a coach to Olsztyn (4 hours) but we could have taken a train which would have taken roughly the same time. This was followed by another bus to Mragowo (1 hour) where we stayed the night in a chalet a the lakeside Cezar campsite. If you go to Mragowo we recommend you eat at the Stara Chata (Old Cottage) restaurant for an example of excellent Polish cuisine.
You could also fly into Gdansk with one of the other budget airlines - Wizz Air and Sky Europe - and then take a train or coach to Olsztyn and Mragowo.

How we arranged the kayak rental..
We simply asked in the Mragowo Tourist Office. This is a grand(ish) building on the opposite side of the road from the bus station next to a large car park. There seems to be a few English speakers working there that were hugely helpful in communicating with the boat hire companies.
There are a number of companies that will hire canoes and kayaks. The cost of hiring the boats is in the region of £5 a day for each boat. However, the company that we hired the boats from seemed to be a fairly amateur outfit. We were picked up by the hire company from next to the Mragowo Tourist Office and taken to Sorkwity where we launched.

How long it took us...
We kayaked over four days. The first and second days were only half-days. The third and fourth days were much more productive.

Where we ate, drank and slept...
• Day One
The first evening we stayed at a pleasant and comfortable guest house on the Lake Dluzec in the village of the same name. The rooms had en-suite bathrooms and later in the season the owners will prepare dinner and breakfast for their guests. As we were a few weeks before the season really kicks off we ate a reasonable meal at the local bar where we were able to get to know the locals a little bit. We played darts and pool and chatted for many hours with Polish people who spoke almost no English which is more Polish than we knew. It was a highly enjoyable evening.
The boats were stored out of the water, out-of-sight and rather close to a protective Rottweiler overnight.

• Day Two
We stayed in Babieta at a SW PTTK waterside 'hotel' in chalet accommodation, which was pretty basic but there was a sink with hot water and bedding provided. We walked into the village and ate at a restaurant next to the river at a point where the boats have to be lifted out to negotiate a weir.

• Day Three
We stopped for lunch in Zgon and ate a splendid little roadside restaurant behind the SW PTTK facility there. The food was good and the restaurant had a number of interesting paintings on the wall alongside a stuffed pheasant and other items.
After a hard afternoon's paddling we made it to Krutyn where we ate at Restaurant Mazurska, which we were reassured was the best place in town to eat and it was indeed pretty good.
We stayed at Hotel Magda, which was very comfortable with en-suite bathrooms. A breakfast of bread, meats, spreads amd fruit was included. The cost was around £11 per person.

• Day Four
We had a simple lunch on the river bank by a bridge bought from a shop in Iznota, before taking on the biggest lake of our adventure. As we paddled towards Mikolajki there was a very prominent yellow hotel with a jetty on the right-side (the east) of the town where we stayed and had the boats collected from. The third floor room had a balcony with a view of the lake and the town.
That night we ate another great meal in a restaurant at a different hotel on the main square. In the peak season I would imagine that there is a lot of choice for places to eat in the town.

Items to take...
In additional to the usual stuff that you might take on one of these types of trip consider some of these:
Large dry sacks (waterproof bags) to keep your stuff dry in the event of a capsize or downpour
Small dry sacks for keeping your documents/camera/money dry and accessible
Polish phrase book with pronunciations
Some form of cushion might be a good idea
Torch
More ideas to follow